Algoasaurus bauri

I'm going to go out on a limb and guess that most of you at best only know of Algoasaurus bauri as a name in a dinosaur genera list or a few lines of text in a comprehensive reference, unless you are from South Africa, are really into sauropods, or just keep track of dinosaur trivia. It had never spent much time in my thoughts until about a week ago, when I was paging through Dinosaurs: The Encyclopedia for some other reason, and I chanced upon the Algoasaurus entry. There, on page 103, was a reprint of the original line drawings from Broom (1904). In the center was a partial neural arch of a posterior dorsal vertebra, and as I glanced at it, it was whispering "Hey, buddy. Yeah, you. Don't I look kind of rebbachisaur-ish?"

From Broom (1904). The "x 1/7" business is not accurate outside of the original paper, but I will say the femur is estimated to have been 50 cm long (20 in) when complete, if that helps.

Normally I do not have 116-year-old line drawings whispering phylogenetic suggestions at me, so I thought I'd look into it a little more. What the heck, I like covering obscure dinosaurs of historic interest anyway.

Algoasaurus bauri was named by Robert Broom in 1904 for a partial skeleton discovered the year before during quarrying operations in Despatch, on the south coast of South Africa. It thus became the very first sauropod described from the continent of Africa. As Anchisaurus can tell you, what the quarry giveth, the quarry taketh away. The quarry workers were not especially interested in the find, and did not separate most of the bones from the clayey rock being used to make bricks, meaning to this day there may well still be bricks in the Nelson Mandela Bay Metropolitan Municipality that contain trace amounts of sauropod. Broom reported that the Port Elizabeth Museum collected "a few fragments of vertebrae and ribs", and that a separate attempt was made to recover more bones still at the site. The formation is now regarded as the Lower Cretaceous Kirkwood Formation (McPhee et al. 2016).

All told, Broom ended up with "a number of very imperfect fragments of vertebrae—cervical, dorsal, and caudal—a fairly good femur, an imperfect scapula, portions of many ribs, and an ungual phalanx". He most frequently compared the bones to Brontosaurus and Diplodocus, which isn't saying much in terms of classification, because at that time the only other reasonably complete sauropod he had to work with was Morosaurus (Camarasaurus). Due to the limited material and the equally limited opportunity for comparisons, Broom did not have much to say about the bones beyond generalities and measurements, although he did note that the femur had a small fourth trochanter and thus a less powerful caudofemoralis than the other known sauropods. He named the animal for Algoa Bay and the then-recently deceased paleontologist George Baur, producing something like "George Baur's Algoa Bay lizard".

From there, A. bauri was met with resounding shrugs, the fate of most sauropods until recent decades. Like some other taxa (Austrosaurus is particularly guilty of this), it made the rounds of the existing groups without finding a firm home; it was generalized enough to fit in almost anywhere, and sauropod classification was generalized enough to accommodate it almost anywhere. Broom gave material from his private collection to the American Museum of Natural History in 1913, including the A. bauri ungual phalanx he mentioned in Broom (1904), where it became AMNH 5631 (Broom 1915; now AMNH FR 5631 if you're searching their database).

A. bauri staged a minor resurgance in the early 2000s. Apparently I'm not the only person to have experienced the phenomenon of the chatty neural arch, because Canudo and Salgado (2003) brought up the apparent absence of a hyposphene as potentially indicating a rebbachisaurid affiliation. And why not? There's some intuitive appeal, after all; it's not a huge sauropod, and it comes from a reasonably appropriate time and place to be a rebbachisaur. The possibility of Algoasaurus being a rebbachisaur was mentioned into the early 2010s (e.g., Ibiricu et al. 2012), but received a solid dumping of cold water in McPhee et al. (2016). Not only could McPhee et al. not classify A. bauri beyond Eusauropoda indet., they couldn't find the type material, besides the AMNH claw and a caudal vertebra that potentially belonged to the type in the collections of the Iziko Museum in Cape Town (SAM-PK-K1500, if you're curious). It seems that Algoasaurus is not something you can set out to find; it just shows up whether you're prepared or not. (Why couldn't Broom have given the AMNH a more useful piece, like, say, that neural arch? Drat.)

So, pending discovery of a new specimen of A. bauri (and being able to make a convincing argument that it *is* A. bauri), or the rediscovery of more of the type, the neural arch of Algoasaurus will just have to whisper in vain. After all, while the neural arch whispers about rebbachisaurs, the scapula, at least as depicted, says "Are you sure about that? You know what a rebacchisaur scapula looks like." (The femur says "What are you looking at me for? I'm just a femoral shaft.")

References

Broom, R. 1904. On the occurrence of an opisthocoelian dinosaur (Algoasaurus Bauri) in the Cretaceous beds of South Africa. Geological Magazine, decade 5, 1(483):445–447.

Broom, R. 1915. Catalogue of types and figured specimens of fossil vertebrates in the American Museum of Natural History. II.–Permian, Triassic and Jurassic reptiles of South Africa. Bulletin of the American Museum of Natural History 25(2):105–164.

Canudo, J. I., and L. Salgado. 2003. Los dinosaurios del Neocomiense (Cretácico Inferior) de la Península Ibérica y Gondwana occidental: implicaciones biogeograficas. Pages 251–268 in F. Pérez-Lorente, editor. Dinosaurios y Otros Reptiles Mesozoicos de España. Instituto de Estudios Riojanos, Logroño, Spain.

Ibiricu, L. M., G. A. Casal, M. C. Lamanna, R. D. Martínez, J. D. Harris, and K. J. Lacovara. 2012. The southernmost records of Rebbachisauridae (Sauropoda: Diplodocoidea), from early Late Cretaceous deposits in central Patagonia. Cretaceous Research 34:220–232.

McPhee, B. W., P. D. Mannion, W. J. de Klerk, and J. N. Choiniere. 2016. High diversity in the sauropod dinosaur fauna of the Lower Cretaceous Kirkwood Formation of South Africa: implications for the Jurassic–Cretaceous transition. Cretaceous Research 59:228–248.