Pol et al. 2021: Anachronistic look at the origin of the Sauropodomorpha

From the Pol et al. 2021 abstract
“Sauropodomorpha is the first major dinosaurian group that radiated during the Triassic.”

No. That’s not how it works in phylogenetic analysis. Clades don’t radiate alone without a second clade also radiating.

Here’s how it works: From a basal clade, llike Dinosauria (represented by Herrerasaurus), there is always a dichotomy where one branch, like Theropoda (represented by Tawa), splits from the another branch, like Phytodinosauria (represented by Buriolestes). This happens in all phylogenetic analyses as it does in the large reptile tree (LRT 1793+ taxa). Rarely three branches arise to produce an unresolved node. That usually means a mistake in scoring. Such a node is not present in this subset  of the LRT focusing on Sauropodomorpha (Fig. 1).

Figure 2. Subset of the LRT focusing on basal phytodinosauria. Aardonyx nests with Saturnalia here.

Figure 1. Subset of the LRT focusing on basal phytodinosauria. Aardonyx nests with Saturnalia here. The Sauropodomorpha is the sister clade to Ornithischia (cropped off the bottom of the graphic).

From the abstract:
“Sauropodomorpha is one of the three major groups of Dinosauria, along with Theropoda and Ornithischia (Benton, 1983; Novas, 1996), and became the most conspicuous herbivores of terrestrial ecosystems of the Mesozoic.”

Again, this is anachronistic paleontology. There are never three major groups of any vertebrate. There should always be dichotomies. Pol et al. need to add taxa to understand the first dichotomy in the Dinosauria splits the Theropoda from the Phytodinosauria. Several nodes later a dichotomy splits Sauropodomorpha from Ornithischia. Both are plant eaters.

Figure 2. Plateosaurus skeleton digitized.

Figure 2. Plateosaurus skeleton digitized.

From the abstract
“These early lineages are currently referred as basal or early sauropodomorphs (Bronzati, 2017) or more traditionally grouped in Prosauropoda (Sereno, 1999; Galton and Upchurch, 2004), a term now in disuse as most phylogenetic studies in the last decade agree in the paraphyly of this group.”

The first dichotomy in Sauropodomorpha in the LRT splits taxa leading to Plateosaurus (Plateosauridae Marsh 1895 = Prosauropoda Huene 1920, Sereno 1998, Fig. 2) from taxa leading to Brachiosaurus.

Recently Baron, Norman and Barrett 2017 were unable to recover basal Phytodinosauria due to taxon exclusion. They also mixed up basal sauropods with basal plateosaurs.

Figure 1. Tiny forelimbs with three sharp-clawed fingers indicate that Guaibasaurus is a theropod, not a sauropodomorph. Shown to scale with related theropods Marasuchus and Procompsognathus.

Figure 3. Tiny forelimbs with three sharp-clawed fingers indicate that Guaibasaurus is a theropod, not a sauropodomorph. Shown to scale with related theropods Marasuchus and Procompsognathus.

Pol et al. report, 
“Guaibasaurus is included in the table although many studies depicted this taxon as an early theropod or saurischian (see text).”

In the LRT Guaibasaurus (Fig. 3) is indeed a basal theropod, so should not have been included in a study focused on phytodinosaurs or sauropodomorphs. That would be like adding pterosaurs to a study focused on archosaurs. Hah! Who would do THAT? (Everyone else, sadly, each time by excluding pertinent taxa).


References
Baron MG, Norman DB and Barrett PM 2017. A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature, 543: 501–506.
Pol D, Otero A, Apaldetti CA and Martinez RJ 2021.
Triassic sauropodomorph dinosaurs from South America: the origin and diversification of dinosaur dominated herbivorous faunas. Journal of South American Earth Sciences. https://doi.org/10.1016/j.jsames.2020.103145

wiki/Plateosauria
https://pterosaurheresies.wordpress.com/2020/11/24/plateosaurus-enters-the-lrt/

Plateosaurus enters the LRT

Perhaps the best known, least controversial dinosaur, 
Plateosaurus engelhardti (von Meyer 1837; Moser 2003; Late Triassic, 210mya; 5-10m in length) is a prosauropod, basal sauropodomorph phytodinosaur. Over 100 skeletons are known. In the LRT Plateosaurus nests in a clade apart from the sauropods and their ancestors. Saturnalia is smaller and older. Aardonyx is larger and later.

Figure 1. Skull of Plateosaurus in several views, colorized here. Note the replacement of the postorbital (amber) with the postfrontal (orange). All sister taxa fuse these bones, so this early illustration may be in error.

Figure 1. Skull of Plateosaurus in several views, colorized here. Note the replacement of the postorbital (amber) with the postfrontal (orange). All sister taxa fuse these bones, and not at that point, so this early illustration may be in error.

In figure 1
note the replacement of the postorbital (amber) with the postfrontal (orange) which uniquely articulates with the squamosal. All sister taxa fuse the postfrontal and postorbital, and not at the stem, so this early illustration may be in error. This character was scored as ‘fused’ based on phylogenetic bracketing. Was I wrong?

Figure 2. Plateosaurus skeleton digitized.

Figure 2. Plateosaurus skeleton digitized by Mallison 2010a, b,

Plateosaurus tracks are known from the Moab desert. Stock photos here.


References
Mallison H 2010a. The digital Plateosaurus I: body mass, mass distribution, and posture assessed using CAD and CAE on a digitally mounted com− plete skeleton. Palaeontologia Electronica13 (2, 8A): 26.
Mallison H 2010b. The digital Plateosaurus II: An assessment of the range of motion of the limbs and vertebral column and of previous reconstructions using a digital skeletal mount. Acta Palaeontologica Polonica 55 (3): 433–458.
Meyer H von 1837. Mitteilung an Prof. Bronn (Plateosaurus engelhardti [message to Prof. Bronn (Plateosaurus engelhardti)]. Neues Jahrbuch für Geologie und Paläontologie (in German). 1837: 316.
Moser M 2003. Plateosaurus engelhardti Meyer, 1837 (Dinosauria, Sauropodomorpha) aus dem Feuerletten (Mittelkeuper; Obertrias) von Bayern [Plateosaurus engelhardti Meyer, 1837 (Dinosauria, Sauropodomorpha) from the Feuerletten (Mittelkeuper; Obertrias) of Bavaria]. Zitteliana Reihe B: Abhandlungen der Bayerischen Staatssammlung für Paläontologie und Geologie (in German and English). 24: 1–186.

wiki/Saturnalia
wiki/Aardonyx
wiki/Plateosaurus

 

Aardonyx (basal sauropodomorph) enters the LRT

Aardonyx celestae 
(Yates et al. 2010; Fig. 1) was originally considered a basal sauropodomodph dinosaur, because it is one.

Figure 1. Aardonyx from Yates et al. 2009. Colors added.

Figure 1. Aardonyx from Yates et al. 20109. Colors added.

In the large reptile tree (LRT, 1760+ taxa; subset Fig. 2) Early Jurassic Aardonyx nests with the Late Jurassic prosauropod, Saturnalia, a taxon not mentioned in the Yates et al. paper. Aardonyx is larger, more robust and has shorter feet, as in sauropods, making it a sauropod mimic.. so, not in the lineage of sauropods. That should be relatively uncontroversial.

Figure 2. Subset of the LRT focusing on basal phytodinosauria. Aardonyx nests with Saturnalia here.

Figure 2. Subset of the LRT focusing on basal phytodinosauria. Aardonyx nests with Saturnalia here.

 

References
Yates AM, Bonnan MF, Neveling J, Chinsamy A and Blackbeard MG 2010. A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism. Proceedings of the Royal Society B. 277(1682): 787–794.

wiki/Saturnalia
wiki/Aardonyx

Saturnalia skull parts!

Bronzati, Müller and Langer 2019 bring us
additional skull data for the basal sauropodomorph, Saturnalia tupiniquim (Fig. 1).

FIgure 1. GIF movie of Saturnalia skull as originally restored and using phylogenetic bracketing to restore a longer rostrum and teeth only anterior to the orbit.

FIgure 1. GIF movie of Saturnalia skull as originally restored and using phylogenetic bracketing to restore a longer rostrum and teeth only anterior to the orbit.

Saturnalia tupiniquim (Langer et al. 1999) Carnian, Late Triassic period, ~225 mya, 1.5 m in length, was one of the oldest true dinosaurs yet found. It was basal to the clade Prosauropoda, 

Figure 1. Grallator illustration from Li et al. 2019 with two basal phytodinosaur possible sisters to the track maker, Pampadromaeus and Saturnalia.

Figure 2. Grallator illustration from Li et al. 2019 with two basal phytodinosaur possible sisters to the track maker, Pampadromaeus and Saturnalia.

The skull was recently described (Bronzati, Müller and Langer 2019). It had a large orbit, like Pantydraco. More cervicals were present and each one was elongated, creating a much longer neck. The scapula was narrow in the middle. The forelimbs were more robust with a large deltopectoral crest on the humerus. The hind limbs were more robust. The calcaneum did not have such a large tuber.

Figure 2. Subset of the LRT focusing on the Phytodinosauria.

Figure 3. Subset of the LRT focusing on the Phytodinosauria.

Adding scores to Saturnalia
provided an opportunity to review scores for other phytodinosaurs in the large reptile tree (LRT, 1568 taxa). These changes resulted in small modifications to the tree topography and higher Bootstrap scores (Fig. 2). Basal phytodinosaurs still give rise to the clades Sauropodomorpha and Ornithischia.


References
Bronzati M, Müller RT, Langer MC 2019. Skull remains of the dinosaur Saturnalia tupiniquim (Late Triassic, Brazil): With comments on the early evolution of sauropodomorph feeding behaviour. PLoS ONE 14(9): e0221387. https://doi.org/ 10.1371/journal.pone.0221387
Langer MC, Abdala F, Richter M, and Benton M. 1999. A sauropodomorph dinosaur from the Upper Triassic (Carnian) of southern Brazil. Comptes Rendus de l’Académie des Sciences, 329: 511-517.
Langer MC 2003. The pelvic and hind limb anatomy of the stem-sauropodomorph Saturnalia tupiniquim (Late Triassic, Brazil). PaleoBios, 23(2): 1-30.

wiki/Saturnalia

Pampadromaeus in exquisite detail

Langer et al. 2019
bring us new data on the basal phytodinosaur, Pampadromaeus (Cabriera et al. 2011; Fig. 1). Pampadromaeus was a small (1m length) biped with a generalized basal dinosaur morphology.

The authors produced a cladogram
(Fig. 2) focusing on Pampadromaeus and kin. Due to taxon exclusion, they considered Pampadromaeus a basal sauropodomorpha. The LRT (subset Fig. 3) nests it as the Late Triassic last common ancestor (LCA) of Sauropodomopha + Ornithischia.

Figure 2. Basal ornithischia and Pampadroameus, a sister to their common ancestor. Daemonosaurus likely resembled Pampadromaeus, with its long neck.

Figure 1. Basal ornithischia and Pampadroameus, a sister to their common ancestor. Daemonosaurus likely resembled Pampadromaeus, with its long neck.

Unfortunately,
Langer et al. are using an old taxon list that is missing many taxa. In the large reptile tree (1406 taxa, LRT, subset Fig. 3) Marasuchus is a basal theropod, not a dinosaur outgroup. Silesaurus is an outgroup poposaur (a dinosaur-mimic), not a sister to Ornithischia. Ornithischia is a dinosaur in-group, nesting with basal phytodinosaurs and sauropodomorphs. Crocodylomorpha (not included in Langer et al.) is the outgroup for the Dinosauria in the LRT.

Figure 2. Cladogram from xx 2019, colors added. Marasuchus is not an outgroup to the Dinosauria. In the LRT it nests as a basal theropod.

Figure 2. Cladogram from xx 2019, colors added. Marasuchus is not an outgroup to the Dinosauria. In the LRT it nests as a basal theropod.

The differences between the tree topologies
in the Langer et al. cladogram and the LRT appear to result largely from the choice of outgroup. In the LRT the outgroups are not chosen, but are recovered from a list of 1400+ taxa. Oddly, some taxa in the LRT are not included in the Langer et al. study. These include Leyesaurus, Barberenasuchus, Eodromaeus, and one specimen of Buriolestes. The LRT includes no suprageneric taxa, like Ornithischia (Chilesaurus, Daemonosaurus, Jeholosaurus and their descendants).

Figure 4. Subset of the LRT focusing on the Phytodinosauria. Three sauropods are added here.

Figure 3. Subset of the LRT focusing on the Phytodinosauria. Three sauropods are added here.

Experiment with outgroups
If the taxon list for the LRT is reduced to more or less match that of Langer et al. 2019, AND Marasuchus is chosen as the outgroup, the result more closely approaches the Langer et al. tree topology (Fig. 4).

Figure 3. Matching the taxon list to that of xx 2019 and choosing Marasuchus for the outgroup results in this cladogram of basal dinosaur relationships.

Figure 4. Matching the taxon list to that of xx 2019 and choosing Marasuchus for the outgroup results in this cladogram of basal dinosaur relationships using LRT data and taxa.

Adding Euparkeria to this list
(Fig. 4) to create a more distant outgroup for  all included taxa moves Silesaurus outside the Dinosauria and moves Marasuchus and Guabisaurus into the Dinosauria. Basically this is what the LRT recovers with a taxon list similar to Langer et al. 2019.

Figure 5. Adding Euparkeria to figure 4 results in this tree where Silesaurus nests outside the Dinosauria, as it does in the LRT. Theropods nest together, as in the LRT. So do phytodinosaurs.

Figure 5. Adding Euparkeria to figure 4 results in this tree where Silesaurus nests outside the Dinosauria, as it does in the LRT. Theropods nest together, as in the LRT. So do phytodinosaurs.

Pampadromaeus barberenai (Cabriera et al. 2011) is a new dinosaur from the Late Triassic of Brazil. It was originally described as a stem sauropodomorph known from a partial disarticulated skeleton and most of the skull bones. The authors reported, “Based on four phylogenetic analyses, the new dinosaur fits consistently on the sauropodomorph stem, but lacks several typical features of sauropodomorphs, showing dinosaur plesiomorphies together with some neotheropod traits.”


References
Cabreira SF, Schultz CL, Bittencourt JS, Soares MB, Fortier DC, Silva LR and Langer MC 2011. New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of Brazil. Naturwissenschaften (advance online publication) DOI: 10.1007/s00114-011-0858-0
Langer MC, McPhee BW, Marsola JCdA, Roberto-da-Silva L, Cabreira SF 2019. Anatomy of the dinosaur Pampadromaeus barberenai (Saurischia—Sauropodomorpha) from the Late Triassic Santa Maria Formation of southern Brazil. PLoS ONE 14(2): e0212543.
https://doi.org/10.1371/journal.pone.0212543
Martínez RN and Alcober OA 2009. A basal sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the early evolution of Sauropodomorpha (pdf). PLoS ONE 4 (2): 1–12. doi:10.1371/journal.pone.0004397. PMC 2635939. PMID 19209223. online article

wiki/Panphagia
wiki/Pampadromaeus

Sauropod nostrils: Where were they?

Short answer:
For whatever reason, derived sauropods shifted the external naris away from the mouth. It would appear illogical to extend soft nostrils back close to the mouth, as Witmer 2001 proposes, over the exterior of the maxillary basin (Fig. 1), which varies greatly (Fig. 2).

Figure 1. From Witmer 2001 showing brachiosaur sauropod skull, colors added. Witmer suggests the nostril might have been located at point 'B' in the maxillary basin (blue) rather than in the external naris (red).

Figure 1. From Witmer 2001 showing brachiosaur sauropod skull, colors added. Witmer suggests the nostril might have been located at point ‘A’ of ‘B’ in the maxillary basin (blue) rather than in the external naris (red).

Witmer 2001 proposed an anterior nostril position
within the nasal basin anterior to the bony external naris in sauropods (positions A and B in Fig. 1, green dot in Fig. 2) and a similar anterior position in other dinosaurs based on an anterior position in most lepidosaurs, crocs and birds. In every photo example presented by Witmer the nostril forms only a small opening relative to the bony external naris.

Witmer 2001 also provided several exceptions to that pattern:

  1. “Cormorant (Phalacrocorax) simply lacked a ßeshy nostril altogether (a diving adaptation)
  2. The bony nostril of geckos is so small that the fleshy nostril occupied almost its entire extent.
  3. The most significant exception was among monitor lizards (Varanus). Some species (e.g., V. griseus, V. dumerili, V. exanthematicus) have a fleshy nostril located in the middle to caudal half of the much enlarged bony nostril.”
  4. Witmer concludes: “Given the diversity of amniotes, one would expect to find additional exceptions.”

As everyone knows,
all tetrapods are capable of inhaling and exhaling through the mouth, which becomes important in panting for internal cooling and when exercise requires more oxygen. The external naris is principally for olfaction and the anterior position of the nostril within the naris maximizes the amount of soft tissue that can be exposed to incoming odors and pheromones.

Figure 1. Four sauropods with external nares identified in pink, internal nares in blue.

Figure 2. Four sauropods with external nares identified in pink, internal nares in blue, Witmer’s proposed nostril in green. Note the external naris already forms a restriction to the airway. For whatever reasons, more derived sauropods phylogenetically shift the nares away from the mouth. Thus there seems to be little reason to imagine the nostrils maintaining an anterior position, nor any reason to further restrict the dimensions of the nostril. When dipping the head down to drink, the internal naris were able to fill with water that drained into the throat whenever the skull was elevated.

A tracing of the external and internal nares in sauropods
(Fig. 2) and a simplified guess connecting the two in lateral view, shows

  1. the elevation of the external naris (pink) relative to the internal naris (blue)
  2. the spacious airway (blue) in sauropod skulls.
  3. the reduced airway proposed by Witmer (green) if skin extended the external naris to the anterior nasal basin
  4. the easy drainage of rainwater if allowed to directly enter the nostrils (pink) in sauropods (probably unimportant, but thought I’d mention it since most nostrils/nares, except whales and crocs, are anterior to lateral, not dorsal)
  5. When dipping the head down to drink, the internal naris were able to fill with water that drained into the throat whenever the lips were sealed and the skull was elevated. That is marginally different from the ostrich drinking behavior (below).
  6. Based on the ostrich example, the sauropod nostril may have extended from 1/3 to 2/3 the area of the external naris in brachiosaurs, to the entire naris in the relatively small external naris of Diplodocus (Fig. 2).

Witmer 2012 (YouTube video below)
provided an ostrich skull in which tissue labeled ‘airway’ completely filled the external naris.

Unfortunately,
the Witmer video does not show the nostril seen in an ostrich photo (Fig. 3). Confusing. That should have been somehow clarified, because the nostril is present in vivo, not in the µCT scan. Added January 22, 2019: The external naris above is the yellow patch at the far anterior tip of the naris. Thank you JB.

Figure 3. Ostrich skull compared to ostrich head with nostril appearing within the external naris.

Figure 3. Ostrich skull compared to ostrich head with nostril appearing within the external naris. The skull may belong to a younger ostrich with a higher cranium than the adult shown here. Note the nostril is about 1/3 the size of the external naris. This may be instructive considering the small head on the end of a long neck on this ostrich, comparable to the small head and long neck in sauropods.

Added January 22, 2019: The following image of a young ostrich
still does not fit the Witmer 2001 ostrich skull. Even when distorted to fit the skull (Fig. 4) the naris does not match the red patch provided for clarification. Something is wrong here. Who can help?

Figure 4. Baby ostrich naris still does not match patch from Witmer 2012 video.

Figure 4. Baby ostrich naris still does not match patch from Witmer 2012 video.

The small head on the end of a long neck
of an ostrich is analogous to the small head and long neck of sauropods when it comes to breathing and drinking. In the ostrich the nostril is one third the size of the naris and located within the naris, more or less anteriorly. Drinking would have been similarly done, with similar problems to get over, like transferring a throat-full or snout-full of water to the stomach by elevating the head and neck.

In a future post
we’ll look, from a scientist’s perspective, why scientists shy away from attempting to replicate discoveries. On the other hand, I revel in testing published hypotheses because so often they leave their work unfinished or misguided one way or another. All the loose ends need to be tidied up.

References
Witmer LM 2001. Nostril position in dinosaurs and other vertebrates and its significance for nasal function. Science 293, 850-853. PDF

Macrocollum enters the LRT

Figure 1.Macrocollum reconstructed alongside various bones From Müller et al. 2018.

Figure 1.Macrocollum reconstructed alongside various bones From Müller et al. 2018.

Macrocollum itaquii (Müller et al. 2018; CAPPA/UFSM 0001b; early Norian, Triassic, 225 myap; 3m in length) was originally considered a member of the “Unaysauridae [which] differs from all other sauropodomorphs by a substantial cranial expansion of the medial condyle of the astragalus. In addition, a promaxillary fenestra is also unique for the group of sauropodomorphs.” Here, in the LRT,  Macrocollum nests with Efraasia, but shares many traits with Massospondylus. That matches the original phylogenetic analysis.

The species is known
from three closely associated specimens demonstrating gregarious behavior. The skull is quite small relative to the neck and rest of the body, even by sauropodomorphi standards. Atypically manual digit 3 is about as long as digit 2.

References
Müller RT, Langer MC and Dias-da-Silva S 2018. An exceptionally preserved association of complete dinosaur skeletons reveals the oldest long-necked sauropodomorphs. Biol. Lett. 14: 20180633. http://dx.doi.org/10.1098/rsbl.2018.0633

wiki/Efraasia
wiki/Macrocollum

SVP 2018: Study says: Hatchling Massospondylus a likely biped

Earlier we looked at a Massospondlylus embryo and a reconstruction that appeared to be quadrupedal based on various limb and torso proportions (Fig. 1).

FIgure 1. Massospondylus embryo in situ and reconstructed.

FIgure 1. Massospondylus carinatus embryo in situ and reconstructed.

Chapelle et al. ((3 co-authors) 2018 report,
“Our results clearly show that M. carinatus was a biped from hatching, and possessed bipedal skeletal proportions even in ovo.”

This is a judgement call. Up to you.

References
Chapelle KE, et al. 2018. Locomotory shfits in dinosaurs during ontogeny. SVP abstracts.

Rapetosaurus: my what a big pubis you have!!

Rapetosaurus krausei
(Curry, Rogers & Forster, 2001) is a Late Cretaceous titanosaur sauropod that is known from several bits and pieces from 3 adults, plus the majority of a juvenile specimen (Fig. 1). Adult lengths are estimated up to 15 m.

Figure 1. Rapetosaurus in traditional quadrupedal and imagined bipedal poses. Here that giant pubis is carrying a big gut.

Figure 1. Rapetosaurus in traditional quadrupedal and imagined bipedal poses. Here that giant pubis is carrying a big gut.

In the large reptile tree (LRT, 1293 taxa) Rapetosaurus nests with the much taller and longer Diplodocus. Rapetosaurus has a much larger pubis for no better reason than to help support its guts when bipedal.

Figure 2. Rapetosaurus skull compared to other sauropods.

Figure 2. Rapetosaurus skull compared to other sauropods. That long antorbital fenestra on Rapetosaurus appears to be a combination of the maxillary fenestra seen in Tapuiasaurus. Note: every facial bone has less bone in Rapetosaurus.

The down-turned snouts here
reflect their angle relative to the occiput and probably the semi-circular canals.

References
Curry Rogers K and Forster CA 2001. The last of the dinosaur titans: a new sauropod from Madagascar. Nature. 412: 530–534. doi:10.1038/35087566

https://en.wikipedia.org/wiki/Rapetosaurus

The many faces (and bodies) attributed to Camarasaurus

The genus Camarasaurus is known from several species
These display differences in the shapes of their skulls and post-crania (Fig. 1). Distinct from the bipedal or tripodal Diplodocus we looked at yesterday, the general build of this genus suggests it did not rise from all fours. Rather elevation of the great neck enabled high browsing, though not as high as its sister in the LRT, Brachiosaurus

Figure 1. Camarasaurus AMNH 567.

Figure 1. Camarasaurus lentus AMNH 567. Compare to shorter legged SMA 0002 specimen in figure 2.

Once considered a Camarasaurus,
the short-limbed, big pelvis Cathetosaurus (Fig. 2) is certainly related, but distinct from the other camarasaurs.

Figure 2. The SMA0002 specimen attributed to Camarasaurus.

Figure 2. The SMA0002 specimen attributed to Camarasaurus an/or Cathetosaurus. Note the robust elements and short distal limbs.

Not only are the bodies distinct,
so are the skulls (Fig. 3) assigned to this genus.

Figure 3. Several skulls attributed to Camarasaurus to scale. SMA 0002 is the short-limbed Cathetosaurus. Brachiosaurus appears to be a derived camarasaur.

Figure 3. Several skulls attributed to Camarasaurus to scale. SMA 0002 is the short-limbed Cathetosaurus. Brachiosaurus appears to be a derived camarasaur. We’re looking at the inside of the mandible in the DINO 2580 specimen.

As in many genera
for which several specimens are known, it is always a good idea to start with just one rather complete specimen in phylogenetic analysis. Add others as your interest grows.

References
Gilmore CW 1925. A nearly complete articulated skeleton of Camarasaurus, a saurischian dinosaur from the Dinosaur National Monument, Utah. Memoirs of the Carnegie Museum 10:347-384.
Madsen JH Jr, McIntosh JS, and Berman DS 1995. Skull and atlas-axis complex of the Upper Jurassic sauropod Camarasaurus Cope (Reptilia: Saurischia). Bulletin of Carnegie Museum of Natural History 31:1-115.
McIntosh JS, Miles  CA, Cloward KC and Parker JR 1996. A new nearly complete skeleton of CamarasaurusBulletin of the Gunma Museum of Natural History 1:1-87.
McIntosh JS, Miller WE, Stadtman KL and Gillette DD 1996. The osteology of Camarasaurus lewisi (Jensen, 1988). Brigham Young University Geology Studies 41:73-115.
Tschopp E, Wings O, Frauenfelder T, and Brinkmann W 2015. Articulated bone sets of manus and pedes of Camarasaurus (Sauropoda, Dinosauria). Palaeontologia Electronica 18.2.44A: 1-65.