Thoughts on Peterson et al. (2022) paper regarding diplodocid feeding mechanisms

Many scientific papers have published regarding the degree of tooth replacement and wear in diplodocoid and macronarian sauropods, namely diplodocids, Camarasaurus, brachiosaurids, and select titanosaurs for which skull material is known. However, very little attention until recently was paid the patterns of tooth replacement and wear in apatosaurine diplodocids, in no small part because the Apatosaurus louisae skull CM 11162, the undescribed Apatosaurus ajax specimen CMC VP-7180, and the apatosaurine specimen TATE 099 found at the Nail Quarry in Como Bluff, Wyoming in 1996, constitute the only apatosaurine skulls that preserve complete teeth (known cranial material for the Apatosaurus ajax holotype includes a braincase and two quadrates, but that's another story). Recently, Peterson et al. (2022) published a paper describing in detail for the first time TATE 099 from Nail Quarry, offering a comprehensive analysis of patterns of tooth wear and replacement for this specimen and further illuminating the nature of feeding mechanisms among flagellicaudatan diplodocoids. 

The history of the systematic placement of TATE 099 within Diplodocidae is rather interesting. It was first referred to as Apatosaurus sp. when first reported in an abstract by Connely and Hawley (1998), who suggested that Apatosaurus used its jaws in front to back sliding motion to aid in cropping and biting when eating plants. For his part, Bakker (1998) referred TATE 099 to Brontosaurus excelsus and used this specimen to claim that B. excelsus differed from Apatosaurus in having the basitubera situated far behind the occipital condyle, but provided no justification as to why TATE 099 was conspecific with B. excelsus, and due to a lack of overlapping material between TATE 099 and B. excelsus holotype, this taxonomic referral was basically ignored by many authors (e.g. Upchurch et al. 2004; Tschopp et al. 2015). In any case, Peterson et al. point out that the basitubera of Apatosaurus louisiae are positioned anterior to the occipital condyle, similar to the condition in TATE 099, and I'm heartened that the authors recognized Bakker's (1998) referral of TATE 099 to Brontosaurus excelsus as lacking basis, and instead assign it to Apatosaurus sp. based on a widely diverging basipterygoid process greater than 60 degrees and the absence of a basisphenoid/basipterygoid recess, both of which are listed as diagnostic characters for Apatosaurus by Tschopp et al. (2015).

CT scans of the maxillae and premaxillae (left) and dentary (right) of Apatosaurus specimen TATE 099 showing unerupted teeth (from Peterson et al. 2022). 3D scans of the unerupted premaxillary/maxillary and dentary teeth shown at the bottom of figures 10 and 11 in Peterson et al. (2022) are included for convenience.

The discussion section of the paper by Peterson et al. (2022) constitutes the real focus on deciphering the rate of tooth wear and replacement among diplodocids. The unerupted tooth counts for TATE 099 reported by the authors in their description of TATE 099 are 5-8 unerupted tooth crowns per alveolus in the premaxilla, 3-5 unerupted tooth crowns per alveolus in the maxilla, and 1-3 unerupted crowns per alveolus in the dentary. Even though Peterson et al. observe differences between diplodocoids and macronarians in the number of replacement teeth as well as tooth volume, shape, and replacement rate, it is quite noteworthy how the authors point out that the rebbachisaurid Nigersaurus lacks alveolar septae and has smaller replacement teeth than those of diplodocid taxa despite the both Nigersaurus and TATE 099 being comparable in the maximum number of replacement teeth. However, the authors don't comment on how the number of replacement teeth of the dentary in TATE 099 compares with that of the holotype of the rebbachisaurid Lavocatisaurus from late Aptian-early Albian deposits in Patagonia, because the latter taxon has several replacement teeth preserved in the dentary. When noting that the numbers of premaxillary/maxillary replacement teeth for TATE 099 as well as Apatosaurus premaxilla MWC 8430 and maxilla MWC 6002 described from Mygatt-Moore Quarry in Colorado by McHugh (2018) are similar, but that dentary of TATE 099 has a number of replacement teeth comparable to those of Dicraeosaurus and the macronarian Brachiosaurus, Peterson et al. (2022) propose that diplodocid taxa retained similar numbers of replacement teeth in the dentary, and interpret the higher numbers of replacement teeth in the upper jaw of Apatosaurus compared to those of diplodocines as supporting the hypothesis by McHugh (2018) that the upper jaw of Apatosaurus was more accustomed to crushing tough plant leaves than that of Diplodocus. In retrospect, the difference between apatosaurines and diplodocines in how they used their upper jaw to chew on plant material may provide another hint at morphological differences between these two diplodocid clades, because some distinguishing features between Apatosaurinae and Diplodocinae can be found in the cervical vertebrae (see Tschopp et al. 2015). Although the erupted tooth row of TATE 099 was unavailable for study by Peterson et al., the authors provide a succinct analysis of the degree of tooth replacement in this specimen based on examination of high-fidelity casts of the erupted tooth row and comparisons with the tooth rows of other sauropods because they note that the row-set tooth replacement patterns in diplodocid taxa like  Apatosaurus, Diplodocus, and Galeamopus contrast with the alternating tooth replacement patterns of the basal macronarian Camarasaurus, since the tooth row of TATE 099 has an uneven occlusal margin that creates an uneven distribution of wear facets on the teeth. 

References:

Bakker, R.T. 1998. Dinosaur mid-life crisis: The Jurassic-Cretaceous transition In Wyoming and Colorado. New Mexico Museum of Natural History and Science Bulletin 14:67-76.

Connely, M.V. and Hawley, R. 1998. A proposed reconstruction of the jaw musculature and other soft cranial tissues of Apatosaurus. Journal of Vertebrate Paleontology 18 (suppl. to volume 3): 35A.

McHugh, J.B. 2018. Evidence for niche partitioning among ground-height browsing sauropods from the Upper Jurassic Morrison Formation of North America. Geology of the Intermountain West 5:95-103.  https://doi.org/10.31711/giw.v5.pp95-103

Peterson, J. E., Lovelace, D., Connely, M., and McHugh, J.B., 2022. A novel feeding mechanism of diplodocid sauropods revealed in an Apatosaurine skull from the Upper Jurassic Nail Quarry (Morrison Formation) at Como Bluff, Wyoming, USA. Palaeontologia Electronica 25(2):a21. https://doi.org/10.26879/1216. palaeo-electronica.org/content/2022/3653-apatosaurine-feeding-mechanism

Tschopp, E., Mateus, O., and Benson, R.B.J. 2015. A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda). PeerJ 3:e857.  https://doi.org/10.7717/peerj.857

Upchurch, 

P., 

Tomida, 

Y., and 

Barrett, 

P.M., 2004. 

A new specimen of Apatosaurus ajax (Sauropoda: Diplodocidae) from the Morrison Formation (Upper Jurassic) of Wyoming, USA. 

National Science Museum Monographs 

26: 

1–

107

.

Perijasaurus and implications for Early-Middle Jurassic eusauropod paleobiogeography in the Western Hemisphere

The South American country of Colombia has received some attention in some media outlets because its government beginning in the mid-2010s engaged in peace talks with the Marxist insurgent groups FARC (Revolutionary Armed Forces of Colombia) and ELN (National Liberation Army), leading to a peace agreement with FARC in 2016 under President Juan Manuel Santos that led to FARC abandoning its guerrilla activities and disbanding to allow many of its members to take part in the Colombian political process. Somewhat lost in talk about Colombia, however, is the fact that it has yielded its own Mesozoic tetrapods, including plesiosaurs, marine turtles, ichthyosaurs, and even a titanosauriform sauropod, Padillasaurus. Recently, Rincón et al. (2022) erected the new genus and species Perijasaurus lapaz for a sauropod dorsal vertebra (UCMP 37689) described from the Early to Middle Jurassic La Quinta Formation of eastern Colombia by Langston and Durham (1955), the species name referring to the town of La Paz near which this specimen was excavated and the fact that the 2016 peace agreement between Bogota and FARC made it possible to relocate the site in Colombia that yielded the holotype of P. lapaz. Given that Patagonia has yielded almost all Jurassic sauropod taxa from South America,  and Perijasaurus is quite significant as the first eusauropod from the Hettangian-Callovian interval to described from a locality in the Western Hemisphere north of Patagonia, I am dedicating this post to giving a synopsis of how Perijasaurus affects knowledge of eusauropod paleobiogeography in the Western Hemisphere during the Early-Middle Jurassic interval.

To give an introductory preview of how Perijasaurus affects state-of-the art knowledge of eusauropod paleobiogeography in the Western Hemisphere, it should be noted that the fossil record of Early-Middle Jurassic eusauropods from this region of the world is mostly concentrated in Patagonia, Argentina, with an extreme dearth of sauropod body and trace fossils in localities in the Western Hemisphere outside Patagonia, in contrast to the abundance of eusauropod taxa unearthed in Hettangian-Callovian deposits of East Asia, Europe, Niger, and Madagascar. For instance, fragmentary sauropod remains described from the Toarcian-age La Boca Formation of southwestern Mexico by Fastovsky et al. (1995) and an isolated caudal vertebra from the Summerville Formation of New Mexico (Lucas and Heckert 2000) constituted the only evidence for sauropod body fossils from the Hettangian-Callovian interval in North American until Rivera-Sylva and Espinosa-Arrubarrena (2020) described fragmentary diplodocid remains collected from the Bathonian-Callovian age Otlaltepec Formation in east-central Mexico in the late 1980s. I have always suspected that sampling biases are mostly responsible for the patchy record of sauropod in western North America from the Toarcian-Callovian interval because sauropod trackways are known from Bajocian-Bathonian deposits in Mexico (Ferrusquía-Villafranca et al. 1978, 1995, 1996). Outside Patagonia, dinosaur trackways have been described from Early-Middle Jurassic deposits in southeastern Brazil and northern Chile (see Weishampel et al. 2004), and together with Perijasaurus show that there maybe additional sauropod fossils from fossiliferous Early-Middle Jurassic deposits in South America outside Patagonia waiting to be unearthed or described to science.

Select views of the holotype of Perijasaurus lapaz (UCMP 37689) (after Rincón et al. 2022) 

When placing the phylogenetic position of Perijasaurus obtained by Rincón et al. (2022) in the broader context of eusauropod biogeography during the Toarcian-Callovian interval, it should be pointed out that the recovery of Perijasaurus in a polytomy with Cetiosaurus, Mamenchisauridae, Neosauropoda, Turiasauria, Jobaria, and a non-neosauropod clade formed by Bagualia, Nebulasaurus, Patagosaurus, and Spinophorosaurus raises questions about the timing of the paleogeographical dispersal of some derived eusauropod lineages from Patagonia to the northern Andes, Africa, Australia, and other regions of the worlds from which sauropod taxa dating to the Toarcian-Callovian have been recorded. For instance, the upper unit of the La Quinta Formation that yielded the Perijasaurus lapaz holotype spans the Toarcian-Aalenian boundary, whereas the Cañadón Asfalto Formation that has yielded Bagualia, Patagosaurus, and Volkheimeria plus a few unnamed taxa has been dated to the middle-late Toarcian based on radiometric dating (Pol et al. 2022). Despite the P. lapaz holotype comprising only a single dorsal vertebra, the late Toarcian-early Aalenian age of Perijasaurus combined with the revised age of the Cañadón Asfalto Formation, but also the fact that the mamenchisaurid Tonganosaurus hails from deposits dating to the Pliensbachian, could indicate that eusauropods had immigrated to northern South America and western North America (e.g. Mexico) by the end of the Early Jurassic. In support of this hypothesis, the North American landmass, including present-day Mexico, was mostly attached to South America until the eve of the Middle Jurassic, by which time Pangaea had begun to break up and the Caribbean Seaway started to form, and East Asia was mostly isolated from the Western Hemisphere (Iturralde-Vinent 2003, fig. 1). Moreover, the Bathonian-Callovian age of the Otlaltepec Formation  makes it probable that eusauropods began migrating to Mexico and eventually most of western North America beginning in the Toarcian because the unit of the the La Quinta Formation that has yielded Perijasaurus lapaz is comparable in age to the La Boca Formation, and present-day Mexico and Central America are adjacent to northwestern South America and therefore must have served as a land bridge for tetrapods to disperse into western North America prior to North America breaking away from South America in the Middle Jurassic. Although Rincón et al. (2022) recover a eusauropod clade comprising  Bagualia, Nebulasaurus, Patagosaurus, and Spinophorosaurus, the cladistic analysis by Holwerda et al. (2021) places Patagosaurus as the sister taxon of Cetiosaurus in a monophyletic Cetiosauridae, and the recovery of Spinophorosaurus as a member of Mamenchisauridae by Ren et al. (2023) combined with the Pliensbachian age of Tonganosaurus indicates that more derived eusauropods began achieving a global distribution by the Toarcian-Aalenian. Alternate placements of Perijasaurus within Eusauropoda as sister to either Haplocanthosaurus or the Turiasauria+Neosauropoda clade hinted at by Rincón et al. could hold water in future studies not only due to the P. lapaz holotype comprising a single element but also because the co-existence of the early-diverging eusauropod Archaeodontosaurus and turiasaurian  Narindasaurus in the Bathonian of Madagascar suggests that both basal and derived eusauropods were also coeval in western North America by the late Toarcian/early Aalenian.  

In summary, Perijasaurus is a chronologically important eusauropod taxon for providing new data on the biogeography of basal and derived eusauropods not only because it the oldest eusauropod from a Western Hemispheric locality outside Patagonia but also in that its discovery in northwestern South America provides hints at the timing of the dispersal of eusauropods into western North America given the current dearth of sauropod body fossils in the Hettangian-Callovian interval. Despite the limited amount of material known for the holotype, it demonstrates that eusauropods began spreading into areas of South America and eventually Mexico at lower latitudes over the course of the Toarcian stage of the Early Jurassic due to the presence of sauropod remains from Toarcian and Bathonian-Callovian deposits in Mexico and New Mexico, and thus constitutes the first non-Patagonian eusauropod genus from the Early to Middle Jurassic of the Western Hemisphere. Given that no sauropod body fossils were reported from the Early to Middle Jurassic of western North America until the 1980s, not to mention dinosaur tracks from deposits of Hettangian-Toarcian and Callovian age in Brazil and Chile, Perijasaurus lapaz itself will be of use in helping track the early evolution and paleobiogeography of eusauropods in areas of the Western Hemisphere north of Patagonia, namely the vicinity of the northern Andes and western North America.

Referennces: 

Fastovsky, D.E., Clark, J.M., Strater, N.H., Montellano, M., Hernandez, R., and Hopson, J.A., 1995, Depositional environments of a Middle Jurassic Terrestrial Vertebrate Assemblage, Huizachal Canyon, Mexico. Journal of Vertebrate Paleontology 15(3): 561–575.

Ferrusquía-Villafranca, I., Applegate., S.P., and Espinosa-Arrubarrena, L., 1978. Rocas volcanosedimentarias mesozoicas y huellas de dinosaurios en la región suroccidental pacífica de México. Revista Mexicana de Ciencias Geológicas 2 (2): 150-162.

Ferrusquía-Villafranca, I., Jiménez-Hidalgo, E., and Bravo-Cuevas, V. M., 1995, Jurassic and Cretaceous dinosaur footprints from México: additions and revisions, Journal of Vertebrate Paleontology 15 (Suppl. to No. 3):28A.

Ferrusquía-Villafranca, I., Jiménez-Hidalgo, E., and Bravo-Cuevas, V.M., 1996, Footprints of small sauropods from the Middle Jurassic of Oaxaca, southeastern Mexico. pp. 119-126. In: Morales, M. (ed.), The Continental Jurassic. Museum of Northern Arizona Bulletin 60.

Iturralde-Vinent, M.A., 2003. The conflicting paleontologic versus stratigraphic record of the formation of the Caribbean Seaway. pp. 75–88. In: Bartolini, C.R., Buffler, B.J., and Blickwede, J.F., (eds.), The Circum-Gulf of Mexico and the Caribbean: Hydrocarbon Habitats, Basin Formation, and Plate Tectonics. American Association of Petroleum Geologists Memoir 79: Tulsa, Oklahoma.

Holwerda, F. M., Rauhut, O. W. M., and Pol, D., 2021. Osteological revision of the holotype of the Middle Jurassic sauropod dinosaur Patagosaurus fariasi Bonaparte, 1979 (Sauropoda: Cetiosauridae). Geodiversitas 43 (16): 575-643. https://doi.org/10.5252/geodiversitas2021v43a16. 

Langston, W., Jr., and Durham, J.W., 1955. A sauropod dinosaur from Colombia. Journal of Paleontology 29 (6):1047–1051.

Lucas, S.G., and Heckert, A.B., 2000. Jurassic dinosaurs in New Mexico. New Mexico Museum Of Natural History and Science Bulletin 17:43-46.

Pol, D., Gomez, K., Holwerda, F.H., Rauhut, O.W.M., and Carballido, J.L., 2022. Sauropods from the Early Jurassic of South America and the Radiation of Eusauropoda. pp. 131-136. In: Otero, A., Carballido, J.L., and Pol, D. (eds.), South American Sauropodomorph Dinosaurs. Record, Diversity and Evolution. Cham, Switzerland: Springer. ISBN 978-3-030-95958-6.

Ren, X.X, Jiang, S., Wang, X.R., Peng, G.Z., Ye, Y., Jia, L., and You, H.L., 2023. Re-examination of  Dashanpusaurus dongi (Sauropoda: Macronaria) supports an early Middle Jurassic global distribution of neosauropod dinosaurs. Palaeogeography, Palaeoclimatology, Palaeoecology 610: 111318. doi:10.1016/j.palaeo.2022.111318.

Rincón, A.F., Raad Pájaro, D.A., Jiménez Velandia, H.F., Ezcurra, M.D., and Wilson Mantilla, J.A., 2022. A sauropod from the Lower Jurassic La Quinta Formation (Dept. Cesar, Colombia) and the initial diversification of eusauropods at low latitudes. Journal of Vertebrate Paleontology 42 (1): e2077112. doi:10.1080/02724634.2021.2077112

Rivera-Sylva, H. E., and Espinosa-Arrubarena, L., 2020, Remains of a diplodocid (Sauropoda: Flagellicaudata) from the Otlaltepec Formation Middle Jurassic (Bathonian-Callovian) from Puebla, Mexico. Paleontologia Mexicana 9 (3): 145-150.

Weishampel, D.B., Barrett, P.M., Coria, R.A., Le Loeuff, J., Xu, X., Zhao, X., Sahni, A., Gomani, E.M.P., and Noto, C.R., 2004, Dinosaur distribution. pp. 517-606. In: Weishampel D.B., Dodson, P., and Osmólska, H., (eds.), The Dinosauria, second edition. Berkeley, CA: University of California Press.

The identity of Bashunosaurus revealed

In a few online sources and publications, there is a taxon of eusauropod from the Chinese Jurassic that has been for the most part unnoticed by the paleontological community, Bashunosaurus kaijiangensis. I first heard of Bashunosaurus when I saw this name in the alphabetical index of Justin Tweet's now defunct website Thescelosaurus! (replaced by the Microsoft Excel document Compact Thescelosaurus in 2015) as a nomen nudum, and in his list of non-avian dinosaur species, Olshevsky (2000) noted that Li et al. (1999) attributed the name Bashunosaurus kaijiangensis to "Kuang, 1996" and classified it as being a camarasaurid, but listed it as nomen nudum because of the lack of a description or diagnosis in Li et al. (1999). Oddly, Bashunosaurus is first mentioned in the paper by Ouyang (1989) describing the Middle Jurassic basal macronarian Abrosaurus dongpoi, again without a description or diagnosis. While reading a paper published earlier this month by Dai et al. (2022) describing the new basal macronarian  Yuzhoulong qurensis from the Middle Jurassic Xiashaximiao Formation of Sichuan, I noticed that Bashunosaurus is mentioned a few times in the paper, particularly the description section whereby Yuzhoulong is compared to other eusauropods from the Xiashaximiao Formation, while happening to come upon an overlooked paper by Kuang (2004) in the references list for the Yuzhoulong paper. Since Dai et al. cite Kuang (2004) when they compare Yuzhoulong with Bashunosaurus, I strongly suspected that it formally describes Bashunosaurus kaijiangensis as a new genus and species given the title of the paper. Thanks to a copy of  Kuang (2004) paper kindly provided to me by Ren Xinxin (one of the co-authors of the Yuzhoulong paper), I can confirm that Kuang (2004) officially names Bashunosaurus kaijiangensis as a new taxon, in which case Bashunosaurus is no longer a nomen nudum. Given that many eusauropod taxa from the Middle-Late Jurassic of East Asia are undergoing re-appraisal, this post will re-appraise the systematic placement and diagnosis of Bashunosaurus by Kuang (2004) as a first step to assessing the true systematic relationships of this taxon.

Kuang (2004) assigns the genus Bashunosaurus to the subfamily Camarasaurinae within the family Camarasauridae, making the partial postcranial skeleton KM 20100 the holotype and designating as the paratype a right ilium and caudal segment (KM 20103). The following characters are given by Kuang in his diagnosis for Bashunosaurus kaijiangensis: 12-13 short opisthocoelous cervical vertebrae; well-developing lateral and ventral keels on the cervicals; low neural arch and parapophysis of the cervicals; posterior cervical vertebrae with greater height/length ratios than anterior and middle cervicals; neural spines of the posterior cervicals bifurcated; anterior and middle dorsals robust and opisthocoelous with well-developed lateral and ventral keels; anterior dorsals with low neural spines, neural spines of the first anterior dorsal vertebra with shallow bifurcation; middle dorsals with elongated centra and high neural spines; deep, extremely robust prezygapophysis, postzygapophysis, and diapophysis of the dorsal vertebrae with prominent laminae; pair of suprazygapophyseal lamina projecting upwards into the transverse processes of the dorsal neural spines; middle and posterior dorsal vertebral centra platycoelous with wide, shallow pleurocoels and less prominent lamina; four sacral vertebrae; robust fan-like sacral rib; anterior caudal vertebrae amphicoelous; broad scapula with a narrow cross-section; humerus with well-developed deltopectoral crest; ilium high with a long, robust pubic peduncle; humerus/femur ratio 0.7; tibia/femur ratio 0.6; femur relatively slender.

Anterior dorsal vertebrae of Bashunosaurus, Dashanpusaurus, and Yuzhoulong showing differences between the three taxa in bifurcation of neural spines of first dorsal vertebrae. Clockwise from left to right - Bashunosaurus kaijiangensis holotype (KM 20100) (after Kuang 2004); Dashanpusaurus dongi holotype (ZDM 5028) (after Ren et al. 2022); Yuzhoulong qurensis holotype (CLGRP V00013) (after Dai et al. 2022)

As with the original diagnoses provided for most Chinese sauropods from the Middle and Late Jurassic, the diagnosis of Bashunosaurus by Kuang (2004) offers little in the way of autapomorphic characters as the cited morphological features are widespread among various eusauropod taxa. For instance, almost all eusauropod taxa have opisthocoelous cervical vertebrae, and the bifurcated neural spine of the first dorsal vertebra occurs in the basal macronarians Bellusaurus, Camarasaurus,  Lourinhasaurus, and Yuzhoulong, but also the mamenchisaurid Mamenchisaurus hochuanensis (Young and Zhao 1972; Mocho et al. 2014; Woodruff and Foster 2017; Dai et al. 2022). Opisthocoely in the anterior dorsal vertebrae and amphicoely in the middle dorsal vertebrae is present among diplodocoids, early-diverging basal eusauropods, and the basal macronarian Yuzhoulong (Dai et al. 2022), whereas platycoelous posterior dorsal vertebrae are shared with all non-macronarian eusauropods (Wilson and Sereno 1998). The humerus/femur ratio is similar to that reported for the basal eusauropod Shunosaurus and basal macronarian Camarasaurus, while the tibia/femur ratio is a characteristic of neosauropod clades (Rose 2007, appendix 1). Although not explicitly mentioned in the diagnosis for Bashunosaurus, the degree of bifurcation of the neural spines of the posterior cervical and anterior dorsal vertebrae tends to be more shallow than that of Camarasaurus, and the shallow bifurcation of the first dorsal vertebra is also found in Bellusaurus, Dashanpusaurus, and Yuzhoulong (Dai et al., 2022; Ren et al. 2022). The pleurocoels of the anterior cervicals of Camarasaurus possess sub-dividing accessory septa (='little lamina' of Kuang 2004), in contrast to the absence of accessory septa on the pleurocoels of the anterior cervicals of Bashunosaurus. As noted by Ren et al. (2022), unlike Camarasaurus and Dashanpusaurus, the middle dorsal vertebrae of Bashunosaurus have laterally oriented diapophyses of the middle dorsal vertebrae, and the first anterior dorsal vertebrae possesses dorsal and lateral margins with a sub-rounded outline in anterior view and two slightly dorsolaterally projecting metapophyses with an open ‘V’-shaped outline in anterior view. The shallow bifurcation of the neural spines of the middle dorsal vertebrae also helps distinguish Bashunosaurus from the contemporaneous basal macronarian Yuzhoulong, which lacks any bifurcation of all dorsal neural spines besides that of the first dorsal vertebra, and the middle dorsal neural spine also differs in having a prominently convex distal end (Dai et al. 2022). Therefore, the abovementioned vertebral characteristics cited by Dai et al. and Ren et al. to distinguish this taxon from some eusauropods from the Xiashaximiao Formation indicate that Bashunosaurus kaijiangensis is most probably a valid neosauropod taxon in its own right.

In an attempt to constrain the systematic placement of Bashunosaurus within Eusauropoda, Kuang (2004) distinguishes Bashunosaurus from taxa he assigns to Cetiosauridae by the more complex and robust laminae of the dorsal vertebrae, bifurcated neural spines of the posterior cervical and anterior dorsal vertebrae, and opisthocoelous centra of the anterior dorsal vertebrae, and he excludes this taxon from Brachiosauridae and Mamenchisauridae due to the cervical vertebrae being proportionally shorter and the presence of 13 short cervical vertebrae. The following characters are cited by Kuang (2004) to assign Bashunosaurus to Camarasaurinae: (1) similar number of presacral vertebrae; (2) proportionally short presacral vertebrae; (3) ventral and lateral keels on the posterior cervical centra; and (4) neural spines of posterior cervical and anterior dorsal vertebrae bifurcated. The first character is difficult to evaluate because the neck and dorsal regions of the B. kaijiangensis holotype are incomplete, whereas character 2 is present in other basal macronarians and many non-neosauropod eusauropods, including Shunosaurus, Mamenchisaurus youngi, and Omeisaurus tianfuensis (Ren et al. 2022). Because there are no cervical vertebrae preserved for Yuzhoulong, the presence of ventral and lateral keels on the posterior cervical vertebrae may be tentatively regarded as a localized autapomorphy for Bashunosaurus within basal Macronaria because Kuang (2004) notes that an undescribed referred specimen of the basal macronarian Abrosaurus lacks ventral and lateral keels on the posterior cervicals. On the other hand, the presence of low neural arches on the cervical centra is also found in Dashanpusaurus (Ren et al. 2022), and bifurcated neural spines on the posterior cervical and anterior dorsal vertebrae are widespread among mamenchisaurids and basal macronarians (Dai et al. 2022; Ren et al. 2022). Although the referred specimen of Abrosaurus is yet to be described, Kuang (2004) regards Bashunosaurus as more derived than Abrosaurus but less advanced than Camarasaurus based on features of the presacral vertebrae, including the degree of bifurcation of the posterior cervical and anterior dorsal vertebrae. However, Camarasauridae as used by Kuang (2004) has not been recovered as monophyletic in any phylogenetic context, although Upchurch et al. (2004) consider Abrosaurus a basal macronarian.  Moreover, Dai et al. (2022) and Ren et al. (2022) caution that a re-appraisal of Bashunosaurus and inclusion of this taxon in a cladistic context is necessary to confirm a potential macronarian placement for B. kaijiangensis.

With the revelation that Bashunosaurus kaijiangensis was officially described as a new genus and species in an overlooked 2004 publication, Bashunosaurus joins the list of putative Chinese dinosaur  nomina nuda that were revealed to have been described as new taxa in hitherto-overlooked papers, which includes the stegosaurs Gigantspinosaurus and Yingshanosaurus, but also increases the overall biodiversity of sauropods from the Xiashaximiao Formation to about a dozen species. As is typical with many original descriptions of new Asian sauropod taxa from the Middle to Late Jurassic, the paper describing Bashunosaurus was quite brief and gave little in the way of autapomorphies or unique character combinations,   

References:

Dai, H., Tan, C., Xiong, C., Ma, Q., Li, N., Yu, H., Wei, Z., Wang, P., Yi, J., Wei, G., You, H., and Ren, X., 2022. New macronarian from the Middle Jurassic of Chongqing, China: phylogenetic and biogeographic implications for neosauropod dinosaur evolution. Royal Society Open Science 9 (11). 220794. doi:10.1098/rsos.220794.

Kuang, X.W., 2004. A new Sauropoda from Kaijiang dinosaur fauna in middle Jurassic beds of North-Eastern Sichuan. pp. 40-46. In: Sun, J.W. (eds), Collection of the 90th anniversary of Tianjin museum of natural history. Tianjin, China: Tianjin Science and Technology Press.

Li K., Zhang, Y., and Cai K., 1999. The Characteristics of the Composition of the Trace Elements in Jurassic Dinosaur Bones and Red Beds in Sichuan Basin. Geological Publishing House, Beijing.

Mocho, P., Royo-Torres, R. and Ortega, F., 2014, Phylogenetic reassessment of Lourinhasaurus alenquerensis, a basal Macronaria (Sauropoda) from the Upper Jurassic of Portugal. Zoological Journal of the Linnean Society 170: 875–916

Olshevsky, G., 2000. An annotated checklist of dinosaur species by continent. Mesozoic Meanderings 3:1-157.

Ouyang H., 1989. A new sauropod from Dashanpu, Zigong Co., Sichuan Province (Abrosaurus dongpoensis gen. et sp. nov.). Zigong Dinosaur Museum Newsletter 2: 10-14.

Ren, X.X., Jiang, S., Wang, X.R., Peng, G.Z., Ye, Y., King, L., and You, H.L., 2022. Osteology of Dashanpusaurus dongi (Sauropoda: Macronaria) and new evolutionary evidence from Middle Jurassic Chinese sauropods. Journal of Systematic Palaeontology. 20 (1). 2132886. doi:10.1080/14772019.2022.2132886.

Rose, P.J., 2007. A new titanosauriform sauropod (Dinosauria: Saurischia) from the Early Cretaceous of central Texas and its phylogenetic relationships. Palaeontologia Electronica 10.2.8A: 1-65.

Upchurch, P., Barrett, P.M. and Dodson, P. 2004. Sauropoda. pp. 259-322. In: Weishampel, D., Dodson, P., and Osmólska, H. (eds.), The Dinosauria, 2nd edition. University of California Press, Berkeley.

Wilson, J.A., and Sereno, P.C., 1998. Early Evolution and Higher-Level Phylogeny of Sauropod Dinosaurs. Journal of Vertebrate Paleontology 18 (supp. 2): 1–79.  doi:10.1080/02724634.1998.10011115

Woodruff, D.C., and Foster, J.R., 2017. The first specimen of Camarasaurus (Dinosauria: Sauropoda) from Montana: The northernmost occurrence of the genus. PLoS ONE 12(5): e0177423. https://doi.org/10.1371/journal.pone.0177423 

Young, C.C., and Zhao, X.-J., 1972. Mamenchisaurus hochuanensis sp. nov. Institute of Vertebrate Paleontology and Paleoanthropology Monographs A 8:1-30.

A critical analysis of the Klamelisaurus paper by Moore et al. (2020)

In the 1980s, new eusauropod remains were unearthed in the Middle-Late Jurassic (Callovian-Oxfordian) Shishugou Formation of Xinjiang, and they would be eventually named Bellusaurus sui  Dong, 1990 and Klamelisaurus gobiensis Zhao, 1993, constituting the first eusauropod taxa to be described from Xinjiang since the description of Tienshanosaurus in 1937. Although Klamelisaurus is based on substantial postcranial remains like the vast majority of eusauropod taxa described from the Shaximiao Formation in Sichuan, and it was assigned to a new subfamily, Klamelisaurinae, within Brachiosauridae, its relationship to other Jurassic eusauropods from East Asia was clouded by an outdated diagnosis, the hypothesis about Klamelisaurus being an adult Bellusaurus, and the need for a comprehensive revision of the well-known genera Mamenchisaurus and Omeisaurus, and thus Upchurch et al. (2004) listed Klamelisaurus as Eusauropoda incertae sedis. Recently, Moore et al. (2020) published a redescription of Klamelisaurus based on comparisons with mamenchisaurid taxa, and cladistic analyses of this taxon found it to be a derived member of Mamenchisauridae as suggested by Upchurch et al. (2004), with some topologies recovering it as sister to Euhelopus, the type genus of Euhelopodidae. Given that some cladistic analyses by Moore et al (2020) create some implications for the validity of Euhelopodidae with respect to Mamenchisauridae considering the recovery of Euhelopus as a titanosauriform, I'll go into certain aspects of the paper by Moore et al. (2020) regarding Klamelisaurus, namely conclusions from results of phylogenetic analyses of this taxon.

Cast of the holotype postcranial skeleton of Klamelisaurus gobiensis on display at a museum in Japan, with a skull cast mounted at the front of the cervical region (courtesy of Wikimedia Commons)  

In the systematic paleontology section of their paper, Moore et al. carry out a comprehensive approach to distinguishing Klamelisaurus from other Jurassic eusauropods from East Asia. As correctly noted by the authors, nearly all the characters included by Zhao (1993) in his diagnosis of Klamelisaurus are virtually either plesiomorphic for non-neosauropod eusauropods or present in other mamenchisaurids, similar to the diagnoses given by Dong et al. (1983) for some eusauropod taxa from Sichuan, and among the characters listed by the authors in the revised diagnosis for Klamelisaurus gobiensis, the scabrous, sheet-like anterior extensions of the spinoprezygapophyseal laminae (SPRL) in the middle to posterior cervical vertebrae is most identical to the sheet-like branch of the SPRL in Hudiesaurus  (Upchurch et al. 2021). Notwithstanding the fact that Moore et al. (2018) noted several morphological differences between Bellusaurus and Klamelisaurus which are clearly non-ontogenetic despite the former being based on juvenile specimens, comparison by Moore et al. (2020) of Klamelisaurus with Mamenchisaurus sinocanadorum and Tienshanosaurus provides new insights into non-neosauropod eusauropod diversity in the Shishugou Formation in a few respect. For instance, the anterior caudal vertebrae of Klamelisaurus differ from those of Tienshanosaurus in lacking strong procoely in the anterior caudal vertebrae, given that strong procoely in the anterior and middle caudal vertebrae once used derived titanosaurs is also seen in many mamenchisaurids. Moreover, although the Klamelisaurus gobiensis and Mamenchisaurus sinocanadorum holotypes preserve non-overlapping cervical vertebrae, with four anterior cervicals included in the only known specimen of M. sinocanadorum, the two taxa come from different levels of the Shishugou Formation, indicating that there was some turnover in this geologic unit as far as the non-neosauropod eusauropod record is concerned, with Mamenchisaurus-like taxa from the upper part of the formation.

Bayesian inference-based cladistic analysis of Klamelisaurus by Moore et al. (2020) based on the Carballido et al (2015) matrix. Note that Euhelopus is recovered in the same clade as Klamelisaurus and Mamenchisaurus constructus (type species of Mamenchisaurus), whereas Bellusaurus falls within Macronaria

The results of the phylogenetic analyses conducted for Klamelisaurus gobiensis deserve attention because of the varying cladistic positions of some euhelopodids as well as Bellusaurus (whose precise cladistic position is stymied by the juvenile nature of all Bellusaurus specimens) in those phylogenies (which utilize the data matrices from the cladistic analyses by Carballido et al. 2015 and Gonzalez-Riga et al. 2018). In the implied-weights parsimony analysis based on the Gonzalez-Riga et al. data matrix, Euhelopodidae sensu D'Emic (2012) is recovered as an early-branching clade of Somphospondyli, but the implied-weights parsimony analysis based on the Carballido et al. data matrix as well as the equal-weights parsimony and Bayesian inference analyses recover Euhelopus and a few taxa of euhelopodids within Mamenchisauridae. On the other hand, Bellusaurus is recovered as a macronarian in all the topologies obtained by Moore et al. utilizing the Carballido et al. data matrix, but it is placed as a sister taxon of Diplodocoidea in the equal-weights and implied-weights parsimony analyses utilizing the Gonzalez et al. data matrix and as a sister taxon of Neosauropoda in the Bayesian inference analysis of the Gonzalez et al. data matrix. Although Moore et al. (2018) reserve judgment regarding the exact phylogenetic position of Bellusaurus due to the juvenile nature of specimens of this taxon, the recovery of Bellusaurus as a basal diplodocoid in some analyses is quite novel because until the description of the dicraeosaurid Lingwulong by Xu et al. (2018), no Jurassic diplodocoids were reported from East Asia. Even though Moore et al. acknowledge that Bellusaurus shares a handful of characters with some mamenchisaurids despite being distinct from Klamelisaurus and lacking features expected for juvenile Klamelisaurus, they note several characters that place Bellusaurus among neosauropods: (1) proatlantal facets on the otoccipital; (2) the lack of foramina between the basal tubera and basipterygoid processes; (3) posterior dorsal neural arches with steeply orientated postzygapophyses; (4) vertical struts within the lateral pneumatic foramen of the dorsal centra; (5) lateral branch of the centropostzygapophyseal lamina in middle and posterior dorsal neural arches; (6) a well-developed ambiens process of the pubis; and (7) fibular facet of the astragalus facing posterolaterally. If the recovery of Bellusaurus as a basal diplodocoid in some analyses by Moore et al. holds water in some future cladistic studies, the cranial architecture of Bellusaurus could shed light on how diplodocoids gradually evolved the elongated skull with slender, pencil-like teeth, given that Moore et al. find Turiasauria to fall within Diplodocoidea in both the equal-weights parsimony analysis of the Gonzalez-Riga data matrix and the implied-weights parsimony analysis of the Carballido et al. data matrix. The recovery of a few euhelopodids as sister to derived mamenchisaurids in some analyses by Moore et al., on the other hand, runs counter to previous cladistic studies placing Euhelopodidae sensu D'Emic (2012) at the base of Somphospondyli. Thus, the question arises: why the varying phylogenetic placements of some euhelopodids among the various topologies obtained by Moore et al. (2020)? 

D'Emic (2012) listed bifurcated neural spines and thick, subhorizontal epipophyseal–prezygapophyseal laminae on the cervical vertebrae as unambiguous synapomorphies uniting Euhelopus with Daxiatitan, Erketu, Phuwiangosaurus, Qiaowanlong, and Tangvayosaurus in a monophyletic Euhelopodidae to the exclusion of all other macronarians. The bifurcation of the cervical neural spines occurs in some mamenchisaurids and turiasaurians, but also various neosauropods, while the second character is present only in Erketu,  Qiaowanlong, and Phuwiangosaurus but not Euhelopus, which shares with Klamelisaurus thin epipophyseal–prezygapophyseal lamina passing nearly horizontally across the cervical neural arches. The extended implied-weights parsimony analysis by Moore et al. using the Gonzalez-Riga et al. matrix, despite agreeing with Wilson & Upchurch (2009) and D'Emic (2012) in recovering Euhelopus  inside Somphospondyli, does not recover Daxiatitan within Euhelopodidae sensu D'Emic (2012), and two of the three synapomorphies listed by D'Emic (2012) uniting Phuwiangosaurus as sister to Tangvayosaurus within Euhelopodidae are ambiguous because no caudal material is known for Erketu, Euhelopus, or Qiaowanlong, so it is unclear if those genera possess the synapomorphic caudal characters of Phuwiangosaurus or  Tangvayosaurus. Although Moore et al. note that Euhelopus and Klamelisaurus share a distolingual boss of the dentition, a rugose muscle scar extending anteriorly from the epipophysis to the posterior margin of the spinodiapophyseal fossa and ventrally convex prediapophyseal lamina of the middle and posterior cervical vertebrae, a ventrally bifurcated postzygodiapophyseal lamina of the cervicodorsal vertebrae, and a fourth femoral trochanter positioned near midline of posterior surface, they caution that the topology recovering Euhelopus as part of the "Core Mamenchisaurus-like Taxa" clade is weakly supported due to shared characters between Euhelopus and Klamelisaurus being present in a few members of Mamenchisauridae, raising the possibility of alternative affinities for Euhelopus. Poropat et al. (2022) note that the teeth of Euhelopus  are unusual for somphospondylan taxa in being spatulate-shaped, while a single tooth preserved in a specimen of Phuwiangosaurus siridhornae  described by Suteethorn et al. (2009) differs from non-somphospondylan macronarians in being peg-shaped. Therefore, it is probable that if Euhelopus is non-somphospondylan according to some phylogenetic analyses by Moore et al. (2020), it could be a basal macronarian outside as suggested by the cladistic analysis of Carballido et al. (2015) because Upchurch et al. (2021) note that the basal somphospondylan Yongjinglong also has a distolingual boss of the dentition, and the absence of caudal vertebrae preserved in the Euhelopus zdanskyi holotype raises the question of whether Euhelopus had strong procoely in the anterior and middle caudal vertebrae as in Klamelisaurus. 

References:

Carballido, J. L., Pol, D., Ruge, M. L. P., Bernal, S. P., Paramo-Fonseca, M. E., and  Etayo-Serna, F. 2015. A new Early Cretaceous brachiosaurid (Dinosauria, Neosauropoda) from northwestern Gondwana (Villa de Leiva, Colombia). Journal of Vertebrate Paleontology 35: e980505. doi:10.1080/02724634.2015.980505 

D’Emic, M. D. 2012. The early evolution of titanosauriform sauropod dinosaurs. Zoological Journal of the Linnean Society 166: 624–671. doi:10.1111/j.1096-3642.2012.00853.x

Dong, Z., Zhou, S., and Zhang, Y. 1983. Dinosaurs from the Jurassic of Sichuan. Palaeontologica Sinica, Series C 162: 1–136.

Gonzalez-Riga, B. J., Mannion, P. D., Poropat, S. F., David, O., D, L., and Coria, J. P., 2018. Osteology of the Late Cretaceous Argentinean sauropod dinosaur Mendozasaurus neguyelap: implications for basal titanosaur relationships. Zoological Journal of the Linnean Society 184 (1): 136–181. doi:10.1093/zoolinne/zlx103 

Moore, A. J., Mo, J., Clark, J. M. and Xu, X. 2018. Cranial anatomy of Bellusaurus sui (Dinosauria: Eusauropoda) from the Middle–Late Jurassic Shishugou Formation of northwest China and a review of sauropod cranialontogeny. PeerJ 6: e4881. doi:10.7717/peerj.4881 

Moore, A. J., P. Upchurch, P. M. Barrett, J. M. Clark, and Xu, X., 2020. Osteology of Klamelisaurus gobiensis (Dinosauria: Eusauropoda) and the evolutionary history of Middle–Late Jurassic Chinese sauropods. Journal of Systematic Palaeontology 18 (16):1299–1393.

Poropat, S.F., Frauenfelder, T.G., Mannion, P.D., Rigby, S.L., Pentland, A.H., Sloan, T. and Elliott, D.A., 2022. Sauropod dinosaur teeth from the lower Upper Cretaceous Winton Formation of Queensland, Australia and the global record of early titanosauriforms. Royal Society Open Science 9: 220381.

Suteethorn, S., Le Loeuff, J., Buffetaut, E., Suteethorn, V., Talumbook, C., and Chonglakmani, C., 2009. A new skeleton of Phuwiangosaurus sirindhornae (Dinosauria, Sauropoda) from NE Thailand. pp. 189-215. In: Buffetaut, E., Cuny, G., Le Loeuff, J., and Suteethorn, V. (eds), Late Palaeozoic and Mesozoic Ecosystems in SE Asia. Special Publication 315. London, UK: The Geological Society.

Upchurch, P., Barrett, P. M., and Dodson, P. 2004. Sauropoda. pp. 259–322. In: Weishampel, D.B., Dodson, P., and Osmolska, H. (eds), The Dinosauria, 2nd edition. University of California Press: Berkeley.

Upchurch P., Mannion, P.D., Xu, X., and Barrett, P.M., 2021. Re-assessment of the Late Jurassic eusauropod dinosaur Hudiesaurus sinojapanorum Dong, 1997, from the Turpan Basin, China, and the evolution of hyper-robust antebrachia in sauropods. Journal of Vertebrate Paleontology 41 (4): e1994414. doi:10.1080/02724634.2021.1994414

Wilson, J. A. & Upchurch, P., 2009. Redescription and reassessment of the phylogenetic affinities of Euhelopus zdanskyi (Dinosauria: Sauropoda) from the Early Cretaceous of China. Journal of Systematic Palaeontology 7(2): 199–239. doi:10.1017/S1477201908002691

Xu, X., Upchurch, P., Mannion, P. D., Barrett, P. M., Regalado-Fernandez, O. R., Mo, J., Ma, J., and Liu, H., 2018. A new Middle Jurassic diplodocoid suggests an earlier dispersal and diversification of sauropod dinosaurs. Nature Communications 9: 2700. doi:10.1038/s41467- 018-05128-1

Zhao, X., 1993. A new Middle Jurassic sauropod subfamily (Klamelisaurinae subfam. nov.) from Xinjiang Autonomous Region, China. Vertebrata PalAsiatica 31: 132–138.

The "flightless pterodactyl" that never was: Ornithopsis hulkei

Prior to and during the Victoria era, British fossil hunters came upon huge or peculiar bones of reptiles from Middle Jurassic to Early Cretaceous deposits in England that they interpreted as belonging to huge crocodile-like archosaurs, namely those from the Oolite Group of the Midlands, the Kimmeridge Clay of southern and eastern England, and the Wealden Supergroup of Sussex and the Isle of Wight. For instance, the type specimens of the basal eusauropod Cetiosaurus and the basal titanosauriform  Pelorosaurus were initially thought to have represented gigantic sea-going crocodiles, until more complete finds in the 1870s showed that they were actually dinosaurs and not crocodiles. However, most paleontology gurus overlook the fact that one Early Cretaceous titanosauriform sauropod from the UK, Ornithopsis, was misinterpreted by its describer as belonging not to a huge crocodile-like reptile, but instead as a flightless pterosaur!

Anterior view of the lectotype of Ornithopsis hulkei (NHMUK R28632) (from Owen 1875)

The story of the discovery and naming of Ornithopsis begins in the early 1850s, when an anterior dorsal vertebra was found in the Early Cretaceous (Barremian) Wessex Formation of the Isle of Wight along the English Channel coast of southern England and kept by Gideon Mantell (describer of Pelorosaurus) in his personal fossil collection, before being acquired by the British Museum in 1853 (a year after Mantell's death) and assigned the catalogue number BMNH R28632 (now NHMUK R28632). The dorsal vertebra, however, was not published in the scientific literature until Seeley (1870) erected the name Ornithopsis hulkei for NHMUK R28632 as well as NHMUK R2239, a dorsal vertebra found in the Early Cretaceous (late Valanginian) Tunbridge Wells Sand Formation of West Sussex in the 1820s by Gideon Mantell and misidentified by Owen (1854) as a quadrate of Iguanodon. He noted that NHMUK R28632 and NHMUK R2239 had cavities for air sacs seen in the bones of birds and pterosaurs, and thus surmised that Ornithopsis could be a missing link between pterosaurs and birds, but also possibly allied with dinosaurs, hence the name Ornithopsis meaning "bird face" in Greek.

Sir Richard Owen (1804-1892), who correctly determined that Ornithopsis was a sauropod dinosaur and not a flightless pterosaur

The identification of Ornithopsis as potentially being a flightless pterosaur would not hold water for very long, however. Owen (1875) agreed with Seeley (1870) that NHMUK R2239 was a dorsal vertebra rather than a quadrate, but he rejected Seeley's interpretation of Ornithopsis as a close relative of birds and pterosaurs and instead considered NHMUK R2239 and R28632 to be congeneric with his new sauropod genus Bothriospondylus from the Late Jurassic (Kimmerdgian) Kimmeridge Clay Formation of Wiltshire. The hypodigm for Ornithopsis hulkei was split into two species, with NHMUK R28632 receiving the new name Bothriospondylus magnus and NHMUK R2239 being made the holotype of the new species Bothriospondylus elongatus. For one thing, Richard Owen was a creationist and not a fan of Darwinist thought, so his lack of enthusiasm for Charles Darwin's theory of evolution endeared him to recognize that Ornithopsis belonged to a sauropod and not a pterosaur-like archosaur. Owen also must have been aware that because the Bothriospondylus elongatus holotype is from an older horizon than NHMUK R28632, the two vertebrae were most likely not conspecific. As a matter of fact, a year after he assigned the Ornithopsis hulkei material to Bothriospondylus, Owen (1876) changed his mind about B. magnus being congeneric with the Bothriospondylus type species (B. suffosus) and referred it to the sauropod genus Chondrosteosaurus from the same geologic horizon and location as NHMUK R28632. Forthwith, Ornithopsis would now be recognized not as a flightless pterodactyl, but instead as a member of Dinosauria --- although Richard Owen had been familiar with extinct and extant flightless birds, no one ever found a genuine pterosaur fossil with flightless abilities. 

In the 1860s and 1870s additional sauropod material was uncovered from the Wessex Formation of the Isle of Wight by Reverend William Fox and John Whitaker Hulke, including some vertebrae that would become the type specimens of the titanosauriforms Chondrosteosaurus magnus and Eucamerotus foxi. In his description of the new titanosauriform remains from the Isle of Wight, Hulke (1879) disputed Owen's opinion about the generic name Ornithopsis being misleading by pointing out that the syntypes of O. hulkei were lightly constructed regardless of the reclassification of Ornithopsis as a sauropod. He designated NHMUK R28632 as the lectotype of O. hulkei, making Bothriospondylus magnus a junior objective synonym of Ornithopsis, and the genera Chondrosteosaurus and Eucamerotus (the latter also described from the Isle of Wight) were synonymized with Ornithopsis. Although Hulke (1882, p. 375) treated the holotype of Bothriospondylus elongatus as the O. hulkei lectotype and referred NHMUK R28632 and the type material of Eucamerotus foxi the Wessex Formation of the Isle of Wight to his new species Ornithopsis eucamerotus, the earlier lectotype designation for O. hulkei by Hulke (1879) stands, as pointed out by Lydekker (1888). 

Although Ornithopsis had been wrongly interpreted as a flightless pterosaur when first named in 1870, it was nonetheless one of the first sauropod taxa to be described from the Isle of Wight and the fourth sauropod taxon described from the Early Cretaceous of Europe (after Pelorosaurus, Haestasaurus, and Oplosaurus). On a few occasions, Ornithopsis was synonymized with Pelorosaurus by von Huene (1909), Romer (1956), and Steel (1970) but Blows (1995) noted that the O. hulkei lectotype does not overlap with the holotype of Pelorosaurus conybeari and found Ornihopsis to be a distinct and valid genus of basal titanosauriform (followed by Upchurch et al. 2011).

References:

Blows, W.T., 1995. The Early Cretaceous brachiosaurid dinosaurs Ornithopsis and Eucamerotus from the Isle of Wight, England. Palaeontology 38 (1): 187–197.

Huene, F. v., 1909. Skizze zu einer Systematik und Stammesgeschichte der Dinosaurier. Centralblatt für Mineralogie, Geologie und Paläontologie 1909:12-22.

Hulke, J.W., 1879. Note (3rd) on (Eucamerotus, Hulke) Ornithopsis, H. G. Seeley, = Bothrospondylus magnus, Owen, = Chondrosteous magnus, Owen. Quarterly Journal of the Geological Society 35 (1–4): 752–762.

Hulke, J.W., 1882. Note on the Os Pubis and Ischium of Ornithopsis eucamerotus. Quarterly Journal of the Geological Society 38 (1–4): 372–376.

Lydekker, R. (1888). Catalogue of the Fossil Reptilia and Amphibia in the British Museum (Natural History). Part I. Containing the Orders Ornithosauria, Crocodilia, Dinosauria, Squamata, Rhynchocephalia, and Proterosauria. British Museum (Natural History). Department of Geology. 309 pp.

Owen, R., 1854. Monograph on the Fossil Reptilia of the Wealden Formations. Part II. Dinosauria (Iguanodon).  Monographs of the Palaeontographical Society 8 (27): 1–54.

Owen, R., 1875. Monographs on the British Fossil Reptilia of the Mesozoic Formations. Part II. (Genera Bothriospondylus, Cetiosaurus, Omosaurus). Monographs of the Palaeontographical Society 29 (133): 15–93.

Owen, R., 1876. Monograph on the Fossil Reptilia of the Wealden and Purbeck Formations. Supplement No. VII. Crocodilia (Poikilopleuron) and Dinosauria? (Chondrosteosaurus). Monographs of the Palaeontographical Society 30 (136): 1–7.

Romer, A.S., 1956. Osteology of the Reptiles. University of Chicago Press: Chicago: IL 772 pp. 

Seeley, H.G., 1870. Ornithopsis, a gigantic animal of the Pterodacyle kind from the Wealden. Annals and Magazine of Natural History 5 (4): 305–318.

Steel, R., 1970. Part 14. Saurischia. Handbuch der Paläoherpetologie. Gustav Fischer Verlag: Stuttgart, 87 pp.

Upchurch, P., Mannion, P.D., and Barrett, P.M., 2011. Sauropod dinosaurs. pp. 476–525. In: Batten, D.J. (ed.). English Wealden Fossils. The Palaeontological Association.

Personal thoughts on Amphicoelias paper by Mannion et al. (2021)

During the Bone Wars in the late 1800s, Edward Drinker Cope (1840-1897) and Othniel Charles Marsh (1831-1899) described several sauropod taxa from the Morrison Formation of western North America, with Marsh erecting the most sauropod species from the Morrison. Although several sauropod genera erected by Marsh have stood the taxonomic test of time, like Apatosaurus, Barosaurus, Brontosaurus, and Diplodocus, the only sauropod genus from the Morrison Formation named by Cope whose validity has been upheld is Camarasaurus, while Caulodon has been synonymized with Camarasaurus (but see here). One sauropod genus described from the Morrison Formation by E.D. Cope whose taxonomic status has fluctuated over time, however, is Amphicoelias Cope, 1877. Although Amphicoelias is poorly known in terms of the holotype of its type species, A. altus, being representing by a few elements, one nominal species of Amphicoelias, A. fragillimus, enjoyed conjectural fame as a super-giant diplodocid until Carpenter (2018) drastically reduced the size estimates for this taxon to 102 feet (31 meters) and reclassified it as a rebbachisaurid, erecting the new genus Maraapunisaurus for it. On the other hand, the validity and precise systematic position of Amphicoelias has been debated, with some studies placing it as a basal diplodocoid and others recovering it as diplodocid. Recently, a new paper on the anatomy and systematics of Amphicoelias was published by Mannion et al. (2021), and while it reaffirms the validity of Amphicoelias as upheld by several authors, I have taken the liberty of expressing some thoughts about the Mannion et al. paper regarding Amphicoelias with respect to diagnostic characters, phylogenetic position, and the bearing of studies on Morrison diplodocoid ontogeny upon Morrison sauropod diversity. 

Selected elements of the holotype of Amphicoelias altus (AMNH 5764): posterior dorsal vertebra (top) and right femur (bottom) (from Mannion et al. 2021)

In the section of their paper in which they redescribe the holotype of Amphicoelias altus (AMNH 5764), Mannion et al. list the "femoral shaft with subcircular cross-section" as one of three autapomorphies for Amphicoelias in the revised diagnosis for this taxon, noting that the femur of AMNH 5764 differs from described Morrison diplodocoid taxa in having a ratio of the mediolateral to anteroposterior diameter of the femur being 0.99 to 1.1 (despite a few signs of taphonomic crushing). However, they also note that the dicraeosaurid specimen MOR 592 found in Montana also has a femur whose cross-section is subcircular at the midshaft; in fact, the subcircular cross-section of the femur was used by Wilson and Smith (1996) to justify referring MOR 592 to Amphicoelias and conclude that Amphicoelias was a basal diplodocoid based on cladistic results that were never published. However, Whitlock (2011) assigned MOR 592 to the family Dicraeosauridae due to the presence of a sharp supraoccipital crest and a symphyseal tuberosity on the dentary, although Woodruff & Fowler (2012) and Woodruff et al. (2017) regarded MOR 592 as an immature diplodocine specimen, but nevertheless recovered Amphicoelias as a basal diplodocoid more derived than Haplocanthosaurus and Amazonsaurus. According to Mannion et al. (2021), the ratio of the mediolateral to anteroposterior diameter of the femur of MOR 592 is approximately 1.3, slightly greater than that for Amphicoelias altus, and MOR 592 has a femur with a slightly beveled distal end in contrast to the more pronounced beveling of the distal femur of AMNH 5764. On the other hand, Tschopp et al. (2015) note that the holotype of Brontosaurus parvus (CM 566) also has a subcircular femoral cross-section, while Wilhite (2005) reports that the subcircular femoral cross-section observed in Amphicoelias, the Brontosaurus parvus holotype, and MOR 592 also occurs in a few diplodocid femora from the Dry Mesa Quarry in Colorado. Since Amphicoelias is recovered as either a basal diplodocid by Tschopp et al. (2015) or an apatosaurine diplodocid by Tschopp and Mateus (2017), whereas Amphicoelias is variously recovered as a stem diplodocoid more derived than Haplocanthosaurus or a diplodocid by Mannion et al. (2021), the subcircular femoral cross-section described for Amphicoelias most likely evolved convergently among a few taxa within Flagellicaudata because Amphicoelias altus is distinguished by Mannion et al. (2021) from all other diplodocoids in having the apex of the posterior dorsal neural spine with rounded, non-tapered lateral projections resulting from the expansion of spinodiapophyseal laminae and little material is preserved in AMNH 5764.

Stratigraphic chart of dinosaur localities in the Morrison Formation (from Turner and Peterson 1999). Despite the opinion of some that the diversity of diplodocoids in the Morrison Formation has been inflated, the type localities of Haplocanthosaurus delfsi (CO-5) and Brontosaurus yahnanpin (WY-44) are stratigraphically low in the Morrison Formation, and type locality of Amphicoelias altus (CO-71) is situated near the top of the Brushy Basin Member of the Morrison Formation, being stratigraphically higher than the type localities of Apatosaurus ajax, A. louisae, Brontosaurus excelsus, and B. parvus. Moreover, three different groups of the diplodocoids (haplocanthosaurids, diplodocids, and dicraeosaurids) have been found at the Felch Quarry 1 (CO-3) in Garden Park, Colorado.  

When addressing the question of whether or not some Morrison diplodocoid species are growth stages of well-known taxa as hinted by Woodruff (2019), Mannion et al. stress that the basal position of the genus Haplocanthosaurus within Diplodocoidea is not attributable to ontogeny given that known specimens of H. priscus and H. delfsi are of the adult/near-adult stage. When taking into account the cladistic diversity and stratigraphic distribution of sauropods within the Morrison Formation, it should be noted that Brontosaurus (=Eobrontosaurus) yahnahpin and Haplocanthosaurus delfsi hail from the lower half of the upper part of the Salt Wash Member of the Morrison Formation whereas Amphicoelias altus was found near the top of the Brushy Basin Member (Turner and Peterson 1999, fig. 7) and that no members of Turiasauria or Mamenchisauridae have yet been reported from the Morrison Formation, although the Lourinhã and Tendaguru Formations have yielded members of Diplodocoidea, Macronaria and Turiasauria. Additionally, given that Whitlock and Wilson Mantilla (2020) note that the juvenile diplodocine specimens CM 3452 and CM 11255 (the latter probably Barosaurus; Melstrom et al. 2016) differ from Kaatedocus, Smitanosaurus, Suuwassea, and MOR 592 in lacking a postparietal foramen despite being juveniles, although the adult apatosaurine specimen BYU 17096 has this feature, it is not hard to imagine four dicraeosaurid taxa existing in the Morrison Formation because known specimens of Kaatedocus, Smitanosaurus, and MOR 592 were found in the upper part of the Salt Wash Member and lowermost part of the Brushy Basin Member, whereas Suuwassea probably was found high in the Morrison Formation (Harris and Dodson 2004; Turner and Peterson 1999). While I agree with Mannion et al. (2021) that ontogeny is an important factor to take into account when determining whether small or primitive sauropod specimens from the Morrison Formation are juveniles of existing species or more basal than well-known diplodocids, the assignment of Suuwassea and MOR 592 to Dicraeosauridae by Whitlock (2011) took into account the possibility that the sub-adult status of the Suuwassea holotype was why Suuwassea defied precise classification within Diplodocoidea when first described by Harris and Dodson (2004), while bearing in mind the fact that some characteristics used to refer MOR 592 to Amphicoelias by Wilson and Smith (1996) were likely to be found in other diplodocoid taxa. Moreover, since Brontosaurus yahnanpin was found lower in the Morrison Formation than Amphicoelias or other species of Brontosaurus, it is possible that it is actually more basal than either B. excelsus, B. parvus, or Apatosaurus because the holotype of Amphicoelias altus contains a few skeletal elements and was found in the uppermost layer of the Brushy Basin Member.     

References:

Carpenter, K., 2018. Maraapunisaurus fragillimus, N.G. (formerly Amphicoelias fragillimus), a basal Rebbachisaurid from the Morrison Formation (Upper Jurassic) of Colorado. Geology of the Intermountain West 5: 227–244.

Harris, J.D. and Dodson, P., 2004. A new diplodocoid sauropod dinosaur from the Upper Jurassic Morrison Formation of Montana, USA. Acta Palaeontologica Polonica 49 (2): 197–210.

Mannion P.D., Tschopp E., and Whitlock, J.A. 2021. Anatomy and systematics of the diplodocoid  Amphicoelias altus supports high sauropod dinosaur diversity in the Upper Jurassic Morrison Formation of the USA. Royal Society Open Science 8 (6): Article ID 210377.  doi:10.1098/rsos.210377        

Melstrom, K.M., D’Emic, M.D., Chure, D.J., and Wilson, J.A., 2016. A juvenile sauropod dinosaur from the Late Jurassic of Utah, USA, presents further evidence of an avian style air-sac system. Journal of Vertebrate Paleontology e1111898.

Tschopp, E., Mateus, O., and Benson, R.B.J., 2015. A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda).  PeerJ  3:e857  https://doi.org/10.7717/peerj.857  

Tschopp, E., and Mateus, O., 2017. Osteology of Galeamopus pabsti sp. nov. (Sauropoda: Diplodocidae), with implications for neurocentral closure timing, and the cervico-dorsal transition in diplodocids. PeerJ 5:e3179 https://doi.org/10.7717/peerj.3179

Turner, C.E. and Peterson, F., 1999. Biostratigraphy of dinosaurs in the Upper Jurassic Morrison Formation of the Western Interior, U.S.A. pp. 77–114. In: Gillette, D.D. (ed.), Vertebrate Paleontology in Utah. Utah Geological Survey Miscellaneous Publication 99-1.

Wilhite, D.R. 2005. Variation in the appendicular skeleton of North American sauropod dinosaurs: taxonomic implications. pp. 268-301. In: Tidwell, V., and Carpenter, K. (eds.), Thunder-lizards: the Sauropodomorph dinosaurs. Indiana University Press, Bloomington.

Wilson, J.A., and Smith, M., 1996. New remains of Amphicoelias Cope (Dinosauria: Sauropoda) from the Upper Jurassic of Montana and diplodocoid phylogeny. Journal of Vertebrate Paleontology 16 (supp. to volume 3): 73A.

Whitlock, J. A. 2011. A phylogenetic analysis of Diplodocoidea (Saurischia: Sauropoda). Zoological Journal of the Linnean Society 161: 872–915.

Whitlock, C., and Wilson Mantilla, J., 2020. The Late Jurassic sauropod dinosaur  'Morosaurus’  agilis  Marsh, 1889 reexamined and reinterpreted as a dicraeosaurid. Journal of Vertebrate Paleontology 40  (6) DOI: 10.1080/02724634.2020.1780600

Woodruff, C., and Fowler, D. W. 2012., Ontogenetic influence on neural spine bifurcation in Diplodocoidea (Dinosauria: Sauropoda): A critical phylogenetic character. Journal of Morphology 273: 754–764. 

 

Woodruff, D. C., Fowler, D. W. and Horner, J. R., 2017. A new multi-faceted framework for deciphering diplodocid ontogeny. Palaeontologia Electronica 20.3.43A: 1–53.