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within Brachiosauridae, its relationship to other Jurassic eusauropods from East Asia was clouded by an outdated diagnosis, the hypothesis about Klamelisaurus being an adult Bellusaurus, and the need for a comprehensive revision of the well-known genera Mamenchisaurus and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. 

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