Is Caulodon a synonym of Camarasaurus?

The non-titanosauriform macronarian Camarasaurus is one of the American public's favorite macronarian sauropods from the Jurassic, being thought of as the most common macronarian from the Morrison Formation. Very few sauropod workers, however, have tackled the alpha-taxonomy of the genus and its various constituent taxonomy since the papers by Ikejiri (2005) and Osborn and Mook (1921). The result has been the tendency to treat Camarasaurus as a genus in numerous phylogenies of Sauropoda (Upchurch et al. 2004; Wilson 2002) without a comprehensive analysis of intrageneric variation of the genus.

In recent abstracts published at the SVP 2013 and 2014 meetings, Mateus and Tschopp (2013) and Tschopp et al. (2014) work to address the question of intraspecific variation in Camarasaurus. The abstract by Mateus and Tschopp (2013) deals with a newly discovered camarasaurid (SMA 0002) that is referred to Cathetosaurus lewisi based on shared characters with BYU 9047 (holotype of C. lewisi). On the other hand, Tschopp et al. (2013) conduct a specimen-level analysis of all Camarasaurus specimens including the type specimens of currently recognized species of the genus (C. grandis, C. lentus, and C. supremus). The phylogenetic results reported by Tschopp et al. (2014) seem to not only reaffirm the distinctness of Cathetosaurus from Camarasaurus, but also support the validity of the three historical species of the latter genus.

These preliminary results have prompted me to revisit the synonymy of Caulodon with Camarasaurus performed by Osborn and Mook (1921) and followed by subsequent authors. When placing the two nominal species of Caulodon (C. diversidens and C. leptoganus) in synonymy with Camarasaurus supremus, Osborn and Mook noted that AMNH 5768 and AMNH 5769 were similar to the maxillary teeth of a referred specimen of Camarasaurus supremus (AMNH 5761) in being robust and spatulate-shaped, but were hesitant to rule out the possibility of two different sauropods with spatulate teeth from the Morrison Formation. However, they did not compare the holotypes of Caulodon diversidens and C. leptoganus with the teeth of Giraffatitan or USNM 5730 (referred to Brachiosaurus sp. by Carpenter and Tidwell 1998).

Since the 1921 monograph by Osborn and Mook, robust spatulate teeth have been described for several non-neosauropod and macronarian sauropods, including Europasaurus, Mamenchisaurus, Turiasaurus, Jobaria, and the brachiosaurid skull USNM 5730 (Carpenter and Tidwell, 1998; Marpmann et al. 2014; Ouyang and He 2002; Royo-Torres and Upchurch 2012; Russell and Zheng 1994; Sereno et al. 1999). Given that robust spatulate teeth are no longer considered diagnostic for Camarasaurus supremus or other camarasaurid species and are widely distributed among non-neosauropod and non-titanosauriform sauropods, the synonymy of Caulodon and its nominal species with Camarasaurus supremus should be regarded as untenable and the two Caulodon species instead must be considered nomina dubia at Eusauropoda indeterminate.

Holotype teeth of Caulodon diversidens (left) and C. leptoganus (right) (after Steel 1970)

     
References:

Carpenter, K., and Tidwell, V., 1998, Preliminary description of a Brachiosaurus skull from Felch Quarry 1, Garden Park, Colorado. In: Carpenter, K., Chure, D. J., and Kirkland, J. I. (eds.), The Upper Jurassic Morrison Formation: An Interdisciplinary Study. Modern Geology 23 (2): 69-84.

Ikejiri, T., 2005, Distribution and biochronology of Camarasaurus (Dinosauria, sauropoda) from the Jurassic Morrison Formation of the Rocky Mountain Region. New Mexico Geological Society, 56th Field Conference Guidebook, Geology of the Chama Basin 2005: 367-379.

Marpmann, J., Carballido, J., Sander, P., Knötschke, N. 2014. Cranial anatomy of the Late Jurassic dward sauropod Europasaurus holgeri (Dinosauria, Camarasauromorpha): ontogenetic changes and size dimorphism. Journal of Systematic Paleontology. DOI: 10.1080/14772019.2013.875074

Mateus, O., & Tschopp E. (2013). Cathetosaurus as a valid sauropod genus and comparisons with Camarasaurus. Journal of Vertebrate Paleontology, Program and Abstracts: 173.

Osborn, H. F., and Mook, C. C., 1921, Camarasaurus, Amphicoelias, and other Sauropods of Cope: Memoris of the American Museum of Natural History, new series, v. 3, part 3, p. 249-387.

Ouyang, H., and Ye, Y., 2002, The first mamenchisaurian skeleton with complete skull: Mamenchisaurus youngi: Sichuan Science and Technology Press: Chengdu. 111pp.

Rafael Royo-Torres & Paul Upchurch, 2012, The cranial anatomy of the sauropod Turiasaurus riodevensis and implications for its phylogenetic relationships. Journal of Systematic Palaeontology, 10(3): 553-583.

Russell, D. A., and Zheng, Z., 1994, A large mamenchisaurid from the Junggar Basin, Xinjiang, People’s Republic of China: In: Results from the Sino-Canadian Dinosaur Project. Canadian Journal of Earth Sciences 30: 2082-2095.

Sereno, P, C., Beck, A. L., Dutheil, D. B., Larson, H. C. E., Lyon, G. H., Moussa, B., Sadleir, R. W., Sidor, C. A., Varricchio, D. J., Wilson, G. P., and Wilson, J. A., 1999, Cretaceous Sauropods from the Sahara and the Uneven Rate of Skeletal Evolution Among Dinosaurs. Science 286: 1342-1347.

Steel, R., 1970, Saurischia: Handbuch der Palaoherpetology. Volume 14. Gustav Fischer Verlag.

Tschopp, E., Mateus O., Kosma R., Sander M., Joger U., & Wings O., 2014. A specimen-level cladistic analysis of Camarasaurus (Dinosauria, Sauropoda) and a revision of camarasaurid taxonomy. Journal of Vertebrate Paleontology. Program and Abstracts: 241-242.

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

Wilson, J. A., 2002, Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136: 217-276.

Dreadnoughtus and the true contender for the title of heaviest sauropod

Ever since the 1980s, many dinosaurologists familiar with sauropods have become fascinated by the specter of extravagantly colossal sauropod species, fortified by the discoveries of the giant diplodocids Seismosaurus hallorum (now Diplodocus hallorum) and Supersaurus vivianae in the 1970s and 1980s. When James Jensen announced the discovery of Supersaurus and its junior synonym Ultrasauros, the mainstream media outlets hailed Ultrasauros as the largest and heaviest sauropod that ever lived, and based on the holotype (BYU 9044) and the brachiosaurid scapulocoracoid BYU 9462, Jim Jensen put the estimates of the length and weight of Ultrasauros at 80 to 100 feet long (25 to 30 meters) and 75 tons (75,000 kilograms) respectively. On the other hand, the discoverer of Diplodocus hallorum, David Gillette, estimated the maximum length and weight of D. hallorum at 177 feet long (54 meters) and 125 tons (113,000 kilograms) respectively. However, the giant Morrison sauropods were eclipsed by the Patagonian titanosaurs as regards discussion of the heaviest sauropod taxa, and recent publications (Carpenter 2006; Foster 2003) have put Diplodocus hallorum and Supersaurus vivianae in the 33 to 50 ton range (30,000 to 45,000 kilograms), a far cry from the earlier weight estimates.

Now, the media has seized upon the discovery of the latest giant titanosaur to be described, Dreadnoughtus schrani (Lacovara et al. 2014), by hailing it as probably the biggest and heaviest sauropod ever to have roamed the earth. This discovery has provided a new window into the question of which sauropod was the heaviest that ever lived, but to compare Dreadnoughtus against other contenders for the title of heaviest sauropod (Argentinosaurus, Futalognkosaurus, Puertasaurus), I have the opportunity to discuss various weight and size estimates for the giant Patagonian titanosaurs with respect to Equation 1 devised by Campione and Evans (2012), which extrapolates the weight of a quadrupedal animal from the minimum circumference of the shaft of its humerus and femur.

When using Equation 1 of Campione and Evans (2012) in order to calculate the body mass of Dreadnoughtus, Lacovara et al. (2014) put the body mass estimate of this genus at 65.4 tons (59,291 kilograms), while noting that the body mass of Dreadnoughtus was probably greater taking into account their histological analysis indicating that the holotype (MPM-PV 1156) was not yet fully grown but still massive in terms of body mass. This is well above the weight estimates provided for Giraffatitan brancai by Benson et al. (2014) but less than the body mass estimate of 134.9 tons (122,400 kilograms) provided for the diplodocoid "Amphicoelias" fragillimus by Carpenter (2006), and less than the weight estimated by Mazetta et al. (2004) for the titanosaur "Antarctosaurus" giganteus. (Since the holotype remains of "Amphicoelias" fragillimus [AMNH 5777] have been lost, it is possible that Carpenter's weight estimate for this species is way off by several tons and "A." fragillimus was not as heavy as estimated by Carpenter.) By contrast, the primitive titanosaur Futalognkosaurus and the turiasaur Turiasaurus weighed 42 tons (38,139 kilograms) and 56.1 tons (50,923 kilograms) respectively.



Regarding the body mass of Argentinosaurus, Paul (1994) estimated the weight of Argentinosaurus at 88 to 110 tons (80,000 to 100,000 kilograms), but Mazzetta et al. (2004) revised the weight to 80 tons (73,000 kilograms), while Sellers et al. (2013) put the weight estimate at 91 tons (83,000 kilograms).  Although it is not implausible that Argentinosaurus was bigger and heavier than Dreadnoughtus judging from the size of the referred femur (MLP-DP 46-VIII-21-3), the known material of this taxon comprises only a tiny part of the postcranial skeleton (9.2%), insufficient to give a reliable estimate of the body mass of Argentinosaurus using the body mass formula devised by Campione and Evans (2012). Likewise, another giant titanosaur from Patagonia, Puertasaurus, may have been heavier and bigger than Dreadnoughtus, with an estimated weight of 88 to 110 tons (80,000 to 100,000 kilograms) based on the huge size of the dorsal vertebra (Novas et al. 2005), but the available material is too meagre to give a more accurate body mass estimate and more complete remains are needed to determine the size of Puertasaurus. 

In summary, any possible body mass estimates for "Amphicoelias" fragillimus, Argentinosaurus,  and Puertasaurus should be treated with caution when taking these sauropods as candidates for the title of heaviest sauropod. Since "Antarctosaurus" giganteus has femora preserved in its type material, it could be a viable contender for the title of heaviest sauropod. Therefore, it may be parsimonious to treat "A." giganteus and Dreadnoughtus as the heaviest sauropods known to science given that the holotype of the former species was not yet fully mature.         

Update: A new paper by Bates et al. (2015) suggests that the original weight estimate for Dreadnoughtus was an overestimate and that Dreadnoughtus probably weighed 42.1 tons (38,225 kilograms), rather than 65.4 tons as originally claimed by Lacovara et al. (2014).

Benson RBJ, Campione NE, Carrano MT, Mannion PD, Sullivan C, et al., 2014. Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage. PLoS Biol 12(5): e1001853 doi:10.1371/journal.pbio.1001853.

Campione, N., and Evans, D., 2012. A universal scaling relationship between body mass and proximal limb bone dimensions in quadrupedal terrestrial tetrapods". BMC Biology: 15. doi:10.1186/1741-7007-10-60.

Carpenter, K., 2006. Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus. In Foster, John R.; and Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 36. Albuquerque: New Mexico Museum of Natural History and Science. pp. 131–138.

Foster, J.R., 2003. Paleoecological analysis of the vertebrate fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain region, U.S.A. New Mexico Museum of Natural History and Science Bulletin, 23. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science.

Lacovara, K.J., Ibiricu, L.M., Lamanna, M.C., Poole, J.C., Schroeter, E.R., Ullmann, P.V., Voegele, K.K., Boles, Z.M., Egerton, V.M., Harris, J.D., Martínez, R.D., and Novas, F.E., 2014. A Gigantic, Exceptionally Complete Titanosaurian Sauropod Dinosaur from Southern Patagonia, Argentina. Scientific Reports. doi:10.1038/srep06196.

Mazzetta, G. V., Christiansen, P., Fariña, R. A., 2004. Giants and Bizarres: Body Size of Some Southern South American Cretaceous Dinosaurs. Historical Biology 16 (2-4): 71–83. doi:10.1080/08912960410001715132.

Novas, F.E.,  Salgado, L., Calvo, J., and Agnolin, F., 2005. Giant titanosaur (Dinosauria, Sauropoda) from the Late Cretaceous of Patagonia. Revisto del Museo Argentino de Ciencias Naturales, n.s. 7 (1): 37–41.

Paul, G. S., 1994. Big Sauropods - Really, Really Big Sauropods. The Dinosaur Report. The Dinosaur Society. pp. 12–13.

Sellers, W. I.; Margetts, L.; Coria, R. A. ­B.; Manning, P. L., 2013. March of the Titans: The Locomotor Capabilities of Sauropod Dinosaurs. In Carrier, David. PLoS ONE 8 (10): e78733. doi:10.1371/journal.pone.0078733. PMC 3864407. PMID 24348896.  edit

McPhee et al. (2014) paper on Antetonitrus, part 2: is "Thotobolosaurus" a relative of Antetonitrus?

In part 1 of my review of the McPhee et al. (2014) paper on the osteology of the basal sauropod Antetonitrus, I discussed the definition of Sauropodiformes and Sauropoda within in the context of the analysis by McPhee et al. (2014) regarding Antetonitrus. However, one overlooked aspect of the paper that didn't make anyone notice it was the discussion of the possible affinity of the Maphutseng sauropodomorph (aka "Thotobolosaurus") with Antetonitrus on page 157 of the paper.

The Maphutseng sauropodomorph Kholumolumo, like the Proctor Lake hypsilophodont Convolosaurus and the Dalton Wells quarry iguanodont, has been occasionally mentioned in the literature but only briefly described. It was first reported by Ellenberger and Ellenberger (1956) based on sauropodomorph remains pertaining to a minimum of six individuals collected from from the Late Triassic lower Elliot Formation of Maphutseng, Lesotho in the 1950s. The Maphutseng taxon was discussed by Charig et al. (1965), Ellenberger (1970), and Ellenberger & Ginsburg (1966), who noted its affinities with sauropods relative to other "prosauropods"; Ellenberger (1970) coined the nomen nudum "Thotobolosaurus mabeatae" for the Maphutseng sauropodomorph in his discussion of the fossil record of southern Africa for the Triassic-early Jurassic interval, but never described it in detail. Gauffre (1993) preliminarily re-assessed the Maphutseng sauropodomorph and tentatively referred it to the nomen dubium Euskelosaurus browni, but he later (1996) changed his mind about the attribution of this taxon and described it as a distinct sauropodomorph under the nomen ex dissertationae "Kholumolumosaurus ellenbergerorum".

The remains of Kholumolumo (formerly given the informal names "Thotobolosaurus" and "Kholumolumosaurus") being excavated in Maphutseng, Lesotho.

Note: A number of studies (Peyre de Fabregues and Allain 2016; McPhee et al. 2017) have shown that Antetonitrus is not from the lower Elliot Formation as previously thought, but instead comes from the upper Elliot Formation. Meanwhile, the Maphutseng sauropodomorph has been named Kholumolumo ellenbergerorum by Peyre de Fabrègues and Allain (2020), but is recovered as a basal massopodan and not a close relative of Antetonitrus in the original description.

Charig, A.J., Attridge, J.& Crompton, A.W. 1965.On the origin of the sauropods and the classification of the Saurischia. Proceedings of the Linnean Society 176: 197–221.

Ellenberger, F., and Ellenberger, P. 1956. Le gisement de Dinosauriens de Maphutseng (Basutoland, Afrique du Sud) [The Maphutseng dinosaur locality (Basutoland, South Africa)]. Comptes Rendus de la Société géologique de France 1956:99-101.

F. Ellenberger and L. Ginsburg. 1966. Le gisement de Dinosauriens triasiques de Maphutseng (Basutoland) et l'origine des Sauropodes [The Triassic dinosaur locality of Maphutseng (Basutoland) and the origin of sauropods]. Comptes Rendus de l'Académie des Sciences à Paris, Série D 262:444-447.

Ellenberger, P.. 1970. Les niveaux paléontologiques de première apparition des mammifères primoridaux en Afrique du Sud et leur ichnologie. Establissement de zones stratigraphiques detaillees dans le Stormberg du Lesotho (Afrique du Sud) (Trias Supérieur à Jurassique) [The paleontological levels of the first appearance of primordial mammals in southern Africa and their ichnology. Establishment of detailed stratigraphic zones in the Stormberg of Lesotho (southern Africa) (Upper Triassic to Jurassic). In: S. H. Haughton (ed.), Second Symposium on Gondwana Stratigraphy and Paleontology, International Union of Geological Sciences. Council for Scientific and Industrial Research, Pretoria 343-370.

F.-X. Gauffre. 1993. Biochronostratigraphy of the lower Elliot Formation (southern Africa) and preliminary results on the Maphutseng dinosaur (Saurischia: Prosauropoda) from the same formation of Lesotho. In S. G. Lucas and M. Morales (eds.), The Nonmarine Triassic. New Mexico Museum of Natural History and Science Bulletin 3:147-149.

Gauffre, F. -X., 1996. Phylogenie des dinosaures prosauropodes et etude d’un prosauropode du Trias superieur d’Afrique australe. PhD thesis. Museum National d’Histoire Naturelle, Paris. 156 pp.

 

McPhee, B.W., Bordy, E.M., Sciscio, L., and Choiniere, J.N. 2017. The sauropodomorph biostratigraphy of the Elliot Formation of southern Africa: Tracking the evolution of Sauropodomorpha across the Triassic–Jurassic boundary. Acta Palaeontologica Polonica 62 (3): 441–465.

Peyre de Fabrègues, C., and Allain, R., 2016. New material and revision of Melanorosaurus thabanensis, a basal sauropodomorph from the Upper Triassic of Lesotho. PeerJ 4: e1639. doi:10.7717/peerj.1639.

 

Peyre de Fabrègues, C., and Allain, R., 2020. Kholumolumo ellenbergerorum, gen. et sp. nov., a new early sauropodomorph from the lower Elliot Formation (Upper Triassic) of Maphutseng, Lesotho. Journal of Vertebrate Paleontology 39 (6). DOI: 10.1080/02724634.2019.1732996

 



McPhee et al. (2014) paper on Antetonitrus, part 1: definition of Sauropodiformes

In a paper describing the anatomy of the primitive Triassic sauropod Antetonitrus ingenipes, McPhee et al. (2014) define the clade Sauropodiformes as including all sauropodomorphs more closely related to Sauropoda than to Massospondylus or Plateosaurus, and they slightly retreat from the original systematic placement of Antetonitrus in Sauropoda by treating it as a sauropodiform close to, if not, part of Sauropoda. However, while McPhee et al. summarize the importance of Antetonitrus in highlighting the transition from the sturdy massospondylids and plateosaurids to the bulky and massive sauropods, the use of the definition of Sauropoda sensu Salgado et al. (1997) by the authors should be taken with a grain of salt.

With respect to the cladistic analysis of Sauropod by McPhee et al. (2014), exclusion of Antetonitrus and Lessemsaurus from Sauropoda would render the sauropod clade Gravisauria Allain and Aquesbi, 2008 synonymous with the definition of Sauropoda sensu Salgado et al. (1997). However, Otero and Pol (2013) treat Antetonitrus, Blikanasaurus, and Lessemsaurus as sauropods under the definition of Sauropoda articulated by Allain and Aquesbi (2008), so it makes sense to retain the sauropod classification of Antetonitrus to avoid creating tiresome phylogenetic clade names in future cladistic analyses of basal sauropods because the Early Jurassic sauropodiform Aardonyx is more primitive than the only other non-sauropod sauropodiform clade from southern Africa, Melanorosauridae.

Irrespective of definition of Sauropoda offered by either McPhee et al. (2014) or Allain and Aquesbi (2008), I have decided to straddle the fence and treat Antetonitrus as a true sauropod just for the sake of phylogenetic accuracy and robustness.   

Allain, R. and Aquesbi, N., 2008. Anatomy and phylogenetic relationships of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco. Geodiversitas 30(2): 345-424.

McPhee, B. W., Yates, A. M., Choiniere, J. N. and Abdala, F., 2014. The complete anatomy and phylogenetic relationships of Antetonitrus ingenipes (Sauropodiformes, Dinosauria): implications for the origins of Sauropoda. Zoological Journal of the Linnean Society, 171: 151–205. doi: 10.1111/zoj.12127

Otero, A.; Pol, D., 2013. Postcranial anatomy and phylogenetic relationships ofMussaurus patagonicus (Dinosauria, Sauropodomorpha). Journal of Vertebrate Paleontology 33 (5): 1138-1168. doi:10.1080/02724634.2013.769444. edit

Impressions on validity of Suuwassea

In a paper discussing ontogeny in the neck vertebrae of diplodocids, Woodruff and Fowler (2012) questioned the validity of Suuwassea emilieae and its placement in Dicraeosauridae. For example, they noted that several characters used to place the genus in Dicraeosauridae (tall cervical neural spines and an anterior prominence at the dentary symphysis) are either symplesiomorphic or also found in the juvenile specimen MOR 592 (referred to Amphicoelias sp. by Wilson and Smith 1996). Moreover, the lack of scapulocoracoidal fusion, the slight bifurcation of the cervical neural spines, and the elongation of the foot bones are used by the authors to point to the immature growth status of ANSP 21122. Therefore, Woodruff and Fowler concluded that Suuwassea might be a possible juvenile form of one of other diplodocoids from the Late Jurassic Morrison Formation.

Although ontogeny could explain some of the non-diplodocid characters in Suuwassea, it is important to note several things. First, the postparietal foramen used to place Suuwassea in Dicraeosauridae is also found in the diplodocine diplodocid Kaatedocus siberi (Tschopp and Mateus 2013) and the indeterminate flagellicaudatan braincase MB.R.2387 (Remes 2009). Other putative dicraeosaurid synapomorphies of Suuwassea listed by Whitlock (2011) (sharp sagittal crest on supraoccipital) are also present in Kaatedocus. Given the diplodocid placement of Kaatedocus and the uncertain status of MB.R.2387 within Flagellicaudata, the presence of a postparietal foramen in both Suuwassea and Kaatedocus appears to be a case of convergent evolution because, as pointed by Tschopp and Mateus, the diplodocid Diplodocus skull CM 11255 lacks such a foramen and Suuwassea and Dicraeosaurus have a postparietal foramen smaller than that of Kaatedocus and MB.R.2387.

Even if the holotype of Suuwassea were subadult, it would still be a distinct species judging from available evidence above. It may take future discoveries to confirm or refute the hypothesis by Woodruff and Fowler (2012) regarding the validity of Suuwassea.

Update: The landmark revision of Morrison diplodocid alpha-taxonomy by Tschopp et al. (2015) indicates that some putative dicraeosaurid characters of Suuwassea (e.g. sharp sagittal crest on the supraoccipital) are also found in the diplodocid Galeamopus, but agrees with Whitlock (2011) that Suuwassea is a dicraeosaurid. Whitlock and Wilson Mantilla (2020) also report a postparietal foramen for the newly redescribed Morrison diplodocoid taxon Smitanosaurus (formerly "Morosaurus" agilis) and recover Kaatedocus as a dicraeosaurid rather than a diplodocid. Therefore, a postparietal foramen is clearly a non-ontogenetic trait exclusive to Dicraeosauridae.

Remes, K., 2009. Taxonomy of Late Jurassic diplodocid sauropods from Tendaguru (Tanzania). Fossil Record 12: 23–46.

Tschopp, E. & Mateus, O., 2013. The skull and neck of a new flagellicaudatan sauropod from the Morrison Formation and its implication for the evolution and ontogeny of diplodocid dinosaurs. Journal of Systematic Palaeontology 11 (7): 853-888, DOI: 10.1080/14772019.2012.746589

 

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

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 (3 Suppl.): 73A.

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

 

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

 

 

Quirks in the cladistic analysis of Lourinhasaurus by Mocho et al. (2014)

It's been barely a year since the second of the three Jurassic Portuguese sauropods, the brachiosaurid titanosauriform Lusotitan ataialensis, was put in a cladistic context by Mannion et. al. (2013) ten years after it was recognized as generically distinct from Brachiosaurus and Giraffatitan. Now, Mocho et. al. (2014) have published a paper re-assessing the cladistic position of the third described Portuguese sauropod, Lourinhasaurus alenquerensis, following in the footsteps of Mannion et. al. (2012, 2013) in putting all of Portugal's sauropod taxa in a phylogenetic context. While it's good that Mocho et al. update the osteology of this genus given that the uncertain placement of some macronarian and non-neosauropod taxa previously assigned to Camarasauridae, I happened to notice a few aspects of the phylogenetic analysis of Lourinhasaurus that seem inconsistent with current state-of-the-art knowledge of eusauropod systematics. Therefore, I have had the opportunity to carefully scrutinize the results of the Lourinhasaurus cladistic analyses by Mocho et al. (2014).

For starters, Lourinhasaurus was originally named as a new Apatosaurus species, A. alenquerensis, by Lapparent and Zbyszewski (1957) and later referred to Camarasaurus by McIntosh (1990a), although McIntosh (1990b) did not rule out the possibility of alenquerensis constituting its own genus due to its higher humerus to femur length ratio. Dantas et. al. (1998) removed alenquerensis from Camarasaurus  based on comparisons with known specimens of Camarasaurus and assigned it to a new genus, which they named Lourinhasaurus, while designating a partial postcranial skeleton from Moinho do Carmo among the syntype series as the lectotype for L. alenquerensis. Because the original description of this taxon had a rather inadequate diagnosis, Upchurch et. al. (2004) found it to be in an unstable position in Eusauropoda, raising the question about the precise placement of Lourinhasaurus among derived eusauropods, including neosauropods. 

Cladistic analyses of Lourinhasaurus by Mocho et al. (2014) using the Wilson (2002) matrix (top) and Upchurch et al. (2004) data matrix (bottom). Note that the Lourinhasaurus phylogeny using the Upchurch et al. (2004) matrix is partly flawed because it did not incorporate data from the cladistic analysis of Curry Roger and Forster (2001).  

When comparing the cladistic analyses of Lourinhasaurus by Mocho et. al. (2014) using the Wilson (2002) and Upchurch et al. (2004) data matrices, it's interesting that while both phylogenies recover a monophyletic Camarasauridae formed by Camarasaurus, Lourinhasaurus, and Tehuelchesaurus, the phylogeny based on the Upchurch et al. (2004) data matrix places Nemegtosaurus and Quaesitosaurus

as diplodocoids rather than titanosaurs and Haplocanthosaurus as a basal macronarian rather than a diplodocoid, while failing to support a monophyletic Euhelopodidae sensu D'Emic (2012). However, this is likely due to the failure of Mocho et. al. (2014) to incorporate characters from the cladistic analyses of D'Emic (2012) and Whitlock (2011) but also the redescription of  Nemegtosaurus and  Quaesitosaurus by Wilson (2005) into the data matrix of Upchurch et al. (2004). Indeed, the cladistic analysis of Titanosauria by Upchurch et al. (2004) did not incorporate characters from the data matrix by Curry Rogers and Forster (2001), although those authors did mention that cladistic results from the latter paper If Camarasauridae sensu Mocho et. al. (2014) holds up in future cladistic analyses concerning the interrelationships of non-titanosauriform macronarians, then Lourinhasaurus would be closely related to Camarasaurus as stated by McIntosh (1990). However, putative camarasaurids such as Dashanpusaurus from the Middle Jurassic of Sichuan, eastern China were not included by Mocho et. al. (2014), so it's unclear whether Camarasauridae had a cosmopolitan distribution in the Middle to Late Jurassic.

References:

Curry Rogers, K., and Forster, C.A., 2001. The last of the dinosaur titans: a new sauropod from Madagascar. Nature 412: 530–534.

D'Emic, M.D., 2012. The early evolution of titanosauriform sauropod dinosaurs. Zoological Journal of the Linnean Society 166 (3): 624–671.

Dantas, P., Sanz, J. L., Marques da Silva, C., Ortega, F., dos Santos V.F., and Cachão, M. 1998. Lourinhasaurus n. gen. Novo dinossáurio saurópode do Jurássico superior (Kimmeridgiano superior-Tithoniano inferior) de Portugal. Comunicações do Instituto Geológico e Mineiro 84 (1A): 91-94.

Lapparent, A.F. de and Zbyszewski, G., 1957. Les dinosauriens de Portugal. Mém. Serv. géol. Port. 2: 1-63.

Mannion, P. D., Upchurch P., Mateus O., Barnes R. N., and Jones M. E. H., 2012. New information on the anatomy and systematic position of Dinheirosaurus lourinhanensis (Sauropoda: Diplodocoidea) from the Late Jurassic of Portugal, with a review of European diplodocoids. Journal of Systematic Palaeontology 10(3), 521–551.

Mannion, P. D., Upchurch P., Barnes R. N., and Mateus O., 2013. Osteology of the Late Jurassic Portuguese sauropod dinosaur Lusotitan atalaiensis (Macronaria) and the evolutionary history of basal titanosauriforms. Zoological Journal of the Linnean Society 168: 98–206.

McIntosh, J.S. 1990a. Sauropoda. pp. 345-501. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria. University of California Press, Berkeley.

McIntosh, J.S., 1990b. Species determination in sauropod dinosaurs with tentative suggestions for their classification. pp. 53-69. In: Carpenter, K., and Currie, P.J. (eds) Dinosaur systematics: approaches and perspectives. Cambridge: Cambridge University Press.

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 (4): 875-916.  DOI: 10.1111/zoj.12113  http://onlinelibrary.wiley.com/doi/10.1111/zoj.12113/abstract

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

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

Wilson, J.A., 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136 (2): 215–275.

Wilson, J.A, 2005. Redescription of the Mongolian sauropod Nemegtosaurus mongoliensis Nowinski (Dinosauria: Saurischia) and comments on Late Cretaceous sauropod diversity. Journal of Systematic Palaeontology 3 (3): 283-318. 10.1017/S1477201905001628.