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.

Diplodocus joins the LRT

There are several ways to measure the tallest dinosaur.
One way is to let the long sauropods, like Diplodocus carnegii (Fig. 1; Marsh 1878; Late Jurassic; 25-32 m long), stand on their hind limbs, like their prosaurod ancestors, balanced by a very long narrow whiplash tail of up to 80 vertebrae. While the neck could not be elevated much beyond horizontal (relative to the dorsal vertebrae), by standing on its hind limbs the torso + neck could be elevated.

Figure 1. Diplodocus standing in a typical feeding posture, as in its prosauropod ancestors.

Figure 1. Diplodocus standing in a typical feeding posture, as in its prosauropod ancestors. Diplodocus could potentially increase its feeding height up to about 11m

Wikipedia reports,
“No skull has ever been found that can be confidently said to belong to Diplodocus, though skulls of other diplodocids closely related to Diplodocus are well known.”

Figure 2. Diplodocus skull animation. Note the short chin and voluminous throat.

Figure 2. Diplodocus skull (USNM 2672, CM 11161) animation. Note the short chin and voluminous throat.

The peg-like teeth of Diplodocus
were smaller and fewer than in other sauropods. And the skull was smaller with nares placed higher on the skull. Evidently diplodocids could only handle smaller needles and leaves from conifer trees matching their height. Wikipedia reports, “Unilateral branch stripping is the most likely feeding behavior of Diplodocus.”

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

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

We know of junior diplodocids
(Fig. 5), half the skull length but with relatively larger eyes. Cute!

Figure 5. A small Diplodocus skull to scale with an adult one.

Figure 5. A small Diplodocus skull to scale with an adult one.

References
Marsh OC 1878. Principal characters of American Jurassic dinosaurs. Part I. American Journal of Science. 3: 411–416.

 

At last! Some sauropods enter the LRT.

Overlooked no longer: the clade Sauropoda.
Learning about clade members now for the first time. Three have been added to the large reptile tree (LRT, 1291 taxa): Diplodocus, Camarasaurus and Brachiosaurus (Figs. 1, 4).

Figure 1. Several sauropod skulls to scale with DGS colors on the bones. Here are Shunosaurus, Camarasaurus, Brachiosaurus and Diplodocus.

Figure 1. Several sauropod skulls to scale with DGS colors on the bones. Here are Shunosaurus, Camarasaurus, Brachiosaurus and Diplodocus.

Note:
the antorbital fossa is absent in derived taxa.

Figure 2. Family of Brachiosaurus illustration from A Dinosaur Year 1989.

Figure 2. Family of Brachiosaurus illustration from A Dinosaur Year 1989 (flipped left to right). The original illustration hangs on the wall behind my computer monitor.

Note 2:
The palate of sauropods shows an increasing space allotted to the internal nares. That makes sense given the increased volumes of air passing in and out of the nares of these increasingly gigantic dinosaurs — a volume that has to be several times the volume of the dead air in that long sauropod throat.

Figure 3. Sauropodiform and sauropod palates, Yizhousaurus, Diplodocus, Camarasaurus and Brachiosaurus. The choanae (internal nares) get bigger in sauropods.

Figure 3. Sauropodiform and sauropod palates, Yizhousaurus, Diplodocus, Camarasaurus and Brachiosaurus. The choanae (internal nares) get bigger in derived sauropods.

Other sauropod traits:

  1. Fingers reduced to single phalanx stubs below semi-tubular metatarsals. Only digit 1 retains an ungual and tracks show it was retroverted, dorsal side down, saving the point, oriented medially to posteriorly (Fig. 4).
  2. External nares dorsal with fragile to absent premaxillary ascending process (Fig. 1).
Figure 5. Reconstructions of manus and pes of Camarasaurus SMA0002 from Tschopp et al.

Figure 4. Reconstructions of manus and pes of Camarasaurus SMA0002 from Tschopp et al. 2015.

The LRT
divided dinosaurs into theropods and phytodinosaurs in 2011. Sauropodomorpha is a phytodinosaur clade, the sister clade of the clade Ornithischia (Fig. 5). Currently 5 taxa within the Phytodinosauria precede this split.

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

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

More
on each of these sauropods will come shortly.

References
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.

Sauropods as neotenous prosauropods

In the course of dinosaur evolution
sauropods reverted to quadrupedal locomotion, a trait found in embryo prosauropods, like Massospondylus, Fig. 1), but not in adult prosauropods or their dinosaurian ancestors.

FIgure 1. Massospondylus embryo in situ and reconstructed.

FIgure 1. Massospondylus embryo in situ and reconstructed.

This topic came to mind after seeing the new paper
on the Early Jurassic basal saurpodiform, Yizhousaurus (Zhang et al. 2018, which appears to remain bipedal as an adult; Fig. 2).

Notably, and despite it’s bipedal appearance,
in the large reptile tree (LRT, 1286 taxa), Yizhousaurus nests with the embryo Massospondylus (Fig. 1), not the adult (Fig. 4). Hence the title of this blogpost.

Figure 1. Yizhousaurus is an early Jurassic basal sauropod.

Figure 2. Yizhousaurus the early Jurassic basal sauropod that currently nests with the embryo Massospondylus.

Yes, the skeleton of Yizhousaurus
has much longer hind limbs than front limbs, which shows that the transition to a quadrupedal locomotion was gradual in adults, but the skull has several sauropod traits and the manual digit 1 ungual is no longer a big hook, but a stub, like the other manual unguals.

Figure 2. Skull of Yizhousaurus in several views.

Figure 3. Skull of Yizhousaurus in several views.

Sauropods like Yizhousaurus had their genesis
in the Early Jurassic and their greatest radiation in the Late Jurassic. Some clades extended to the Late Cretaceous.

FIgure 4. Massospondylus adult in situ.

FIgure 4. Massospondylus adult in situ.

Did sauropods have several or a single origin?
I have no idea, but the idea is already floating around out there.

References
Barrett PM 2009. A new basal sauropodomorph dinosaur from the upper Elliot formation (Lower Jurassic) of South Africa. Journal of Vertebrate Paleontology 29(4):1032-1045.
Carrano MT 2005.The evolution of sauropod locomotion: morphological diversity of a secondarily quadrupedal radiation.” in The Sauropods: Evolution and Paleobiology, edited by Curry Rogers, K. A. and Wilson, J. A., 229–251. University of California Press.
Morris J 1843. A Catalogue of British Fossils. British Museum, London, 222 pp.
Reisz RR, Scott D; Sues H-D, Evans DC and Raath MA 2005. Embryos of an Early Jurassic prosauropod dinosaur and their evolutionary significance. Science. 309(5735): 761–764.
Reisz RR, Evans DC, Roberts EM, Sues H-D and Yates AM 2012. Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorph Massospondylus PDF. Proceedings of the National Academy of Sciences of the United States of America. 109(7): 2428–2433.
Riley H and Stutchbury S 1836. A description of various fossil remains of three distinct saurian animals discovered in the autumn of 1834, in the Magnesian Conglomerate on Durdham Down, near Bristol. Proceedings of the Geological Society of London 2:397-399.
Zhang Q-N, You H-K, Wang T and Chatterjee S 2018. A new sauropodiform dinosaur with a ‘sauropodan’ skull from the Lower Jurassic Lufeng Formation of Yunnan Province, China. Nature.com/scientificreports 8:13464 | DOI:10.1038/s41598-018-31874-9

wiki/Massospondylus
wiki/Yizhousaurus