A Fistful of Spinosaurus

When I offered my hint at what Spinosaurus aegyptiacus looked like, here, I did so omitting newer material that had been recovered since the early 1900’s when the holotype was first recovered and described. My preference at the time was simply to offer a peak at a conclusion of the vertebrae, not to show-case further specimens and speculation on the cranial structure. New specimens of cranial material have been described since then, and some of these include portions of the rostrum, including maxilla and premaxilla. These determinately influence the shape of the skull, and indeed the relative functional anatomy of the jaw. If we presume jaw occlusion, how precisely does that work given the material at hand? We lack a complete skull, even though partial skulls are known for other spinosaurid taxa (Charig & Milner, 1986; Taquet & Russell, 1996; Martill et al., 1996; Kellner & Campos, 1996; Sereno et al., 1998) as well as additional taxa that were initially described as non-spinosaurs, but have received some more attention (I will get into these later). None of these are Spinosaurus aegyptiacus, though, and we feel we must reserve ourselves to African specimens, especially those from super-Saharan Africa. There has been an interesting, if understated conclusion regarding the relative closure of the jaw and reconstructions of the skull of Spinosaurus aegyptiacus, and it is to these that I wish to bring attention in this post. Well, not this post, as writing it it became clear it would be excessively long of a single discussion. The title of this post alludes that there will be three posts total, and this is the first.

It has been my opinion for some time that much of the specimens from the north of Africa, be it Algeria, Tunisia, or Morocco, may not actually belong to Spinosaurus aegyptiacus. This is due to a few factors, but the most glaring one of which is that there are no direct overlap of materials that single out the peculiar morphology of the two best described sets of rostrum and the dentary; second, but not far behind, is that the material all come from different times. The sediments of Tunisia and Morocco, for example, are younger by almost 10Ma than those of Egypt from which Spinosaurus aegyptiacus derives.

It is these two facts that make me think that separating the specimens from the West from those of the East is a good, if not very good, idea. But there is an additional reason, and that’s to do with material.

Skeleton of Spinosaurus aegyptiacus von Stromer, 1915, based on the holotype IPHG (BSP) 1912 VIII 19.

Remains attributed to Spinosaurus in Africa comprise almost exclusively teeth gathered from Egypt, Libya, Tunisia, Algeria and Morocco. Depending on the quality and size of these teeth, or the set of mind of the referrer, these teeth may be attributed to Spinosaurus aegyptiacus, Spinosaurus cf. aegyptiacus, cf. Spinosaurus aegyptiacus, Spinosaurus sp., cf. Spinosaurus sp., etc., with decreasing levels of “certainty” involved[n1]. Most of this is due to the fluting on the surfaces of the teeth, but damage to the teeth can cause doubt as to which “level” of referral is useful, or maybe there’s a feature of the dentition (e.g., curvature) which mandates a potential for something not quite Spinosaurus aegyptiacus. As the only named useful “spinosaurine” spinosaurid from Africa, barring the “baryonychine” spinosaurids from Niger (see here for discussion), Spinosaurus aegyptiacus has become something of the only container for which large, unserrated, fluted or non-fluted conical and carinate teeth from Africa would be referable to. No one has asserted yet that there are valuable methods to discriminate the teeth, regardless of the methodology employed by Smith (2005).

Certainly, there is one true affirmative specimen of Spinosaurus aegyptiacus, and that is IPHG 1912 VIII 19, described by Ernst von Stromer in 1915. This specimen, however, does not exist. Or, it doesn’t anymore.

Plates 1 and 2 of von Stromer, 1915. The only published visual renditions of the material produced prior to its destruction.

So we are left with a lost (read: destroyed) holotype for a taxon that we continue to refer specimens to. Problematically, this includes a veritable buttload of teeth, jaw fragments, half-complete skulls, and various pieces of vertebrae. So far, no one has described anything remotely like that of IPHG 1912 VIII 19. This is important, because on the basis of further material from Gara Samani in the Algerian Maghreb, Dale Russell (1996) described a new species, maroccanus, under the Spinosaurus umbrella, for the sake of a cervical vertebral centrum (CMN 50791) and several other specimens of partial vertebrae, mostly centra; fragments of the jaws, and teeth, were additionally referred. This material, differing on the basis of proportions of the vertebrae at the same relative scale, affirmed to Russell a distinct western species. This wasn’t raised on biogeographic grounds, however, although the relative dating of Gara Samani to the Albian cannot be overlooked (Russell, 1996; Tacquet & Russell, 1998) despite suggestions that the Onychopristis numida (von Stromer, 1927) recovery restricts the data to the Cenomanian broadly among virtually all Spinosaurus-teeth-bearing formations of the Saharan and Maghreb deserts (de Broin et al., 1971). The Bahariya Formation of Egypt is dated to the lower Cenomanian, a somewhat younger level than the Gara Samani (Smith et al., 2001).

Taquet & Russell (1998) subsequently described material from the Kem Kem of Morocco (also from the lower Cenomanian, and thus roughly the same age as the Bahariya deposits) which included a fused pair of premaxillae attached to conjoined but unfused rostral maxillae (MNHN SAM 124). Portions of premaxillae and maxillae and dentaries are known, most of this from the Kem Kem or elsewhere in Morocco and Algeria, as well as specimens noted from Libya, Tunisia, Kenya, Niger, and so on. I won’t summarize it.

You’d need Therizinosaurus-sized fists to hold this many Spinosaurus.

A jaw fragment was located in a private collection and subsequently acquired by the Museo di Storia Naturale in Milano (MSNM V4047) which consists of about half or more of the entire front upper jaw (dal Sasso et al., 2005). Rather than support Russell’s taxonomy, dal Sasso et al. chose to reject the distinctiveness of maroccanus and labelled it a “nomen dubium,” and stated that there should only be one species from the Albian to Cenomanian of North Africa, on the basis of an apparent lack of substantive variation in the collected material. This effectively refers all material of Russell (1996) and Taquet & Russell (1998) to Spinosaurus aegyptiacus, and included their new upper jaw and a fragment (UCPC-2) recognized as a formerly uncataloguable fragment from the University of Chicago, part of Paul Sereno’s expeditions to the Kem Kem. This effectively lumped the species, although maroccanus still “stands.” As an additional note, dal Sasso et al. inferred the placement of the privately collected MSNM V4047 would have derived from the Kem Kem due to relative preservation and matrix color, as well as a vertebra referred to Onychopristis, a fossil sawfish; with the prevalence of Onychopristis numida across the Saharan, from the Bahariya basin easterly to the Maghreb to the High Atlas of Morocco, it is possible the jaw fragment may derive from more broadly an area than specifically the Kem Kem.

With just one species available, Spinosaurus aegyptiacus became the principle container of north African spinosaur material. This understates the potential to variation, and raises the problems of issues dealing with lost or damaged holotypes which reamin unavailable for use to compare to new specimens.

In the next post on this topic, I will continue discussion of additional specimens referred to Spinosaurus aegyptiacus, and their problems.

[n1] I do not give much value to the varying degrees of certainty here, as they typically require qualifying the differences between “genus” and species, or higher rank taxa. “Confer” is typically meant to imply a referral with a suggestion of close affinities, without commitment. However, this type of “referral” is silly: it either is referred, or it is not, and there should be no middle ground. If one cannot refer a specimen to a particular clade, it should simply be referred to the narrowest clade possible the authors have certainty of.

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