Sigilmassasaurus

*Sigilmassasaurus brevicollis*

***Sigilmassasaurus*** (meaning “Sijilmassa lizard”) is a genus of spinosaurid dinosaur from Northern Africa, living in the early Cretaceous. It is thought to have looked a bit like *Spinosaurus*, which lived in the same place and time. Not much is known about the animal, although it was likely fairly large.

This theropod, by far has had a complicated taxonomic history, occasionally being considered synonymous with other dinosaurs and at times being considered a valid genus.

Fossils of this dinosaur were found in the Tafilalt Oasis region of Morocco, near the site of the ancient city of Sijilmassa, for which it was named. Canadian paleontologist Dale Russell named *Sigilmassasaurus* in 1996, from the ancient city and the Greek word sauros (“lizard”). A single species was named, *S. brevicollis*, which is derived from the Latin brevis (“short”) and collum (“neck”), because the neck vertebrae are very short from front to back. Russell also described another specimen as a possible second species of *Sigilmassasaurus*, although he chose not to name it due to its incomplete nature.

*Sigilmassasaurus* comes from sediments in northwest africa, southern Morocco, which are called by various names, including the Gres rouges infracenomaniens, Continental Red Beds, and lower Kem Kem Beds. These rocks date back to the Cenomanian, the earliest faunal stage within the Late Cretaceous Period, or about 100 to 94 million years ago (Sereno et al., 1996).

Further studies validated the possiblity of a second Spinosaurid within the Kem Kem formation. Based off from highly differentiated vertebrae.

## Disputed validity

The holotype, or original specimen, of S. brevicollis is a single neck vertebra, although Russell referred about fifteen other vertebra found in the same formation to the species. Other material was found in Egypt, and is known as “Spinosaurus B” (Stromer, 1934). Russell considered this Egyptian specimen to belong to *Sigilmassasaurus* or a closely related animal, and created the family Sigilmassasauridae for these animals (Russell, 1996). The neck vertebrae of these dinosaurs are wider from side to side than they are long from front to back. The exact position of *Sigilmassasaurus* within the theropod family tree is unknown, but it belongs somewhere inside the theropod subgroup known as Tetanurae.

Some scientists do not believe that *Sigilmassasaurus* is a valid genus. In 1996, Paul Sereno and colleagues described a *Carcharodontosaurus* skull (SGM-Din-1) from Morocco, as well as a neck vertebra (SGM-Din-3) which resembled that of “Spinosaurus B,” which they therefore synonymized with *Carcharodontosaurus* (Sereno et al., 1996). A later study went further, calling *Sigilmassasaurus* itself a junior synonym of *Carcharodontosaurus* (Sereno et al., 1998).

More recently, however, it was revealed that SGM-Din-3, which was used to synonymize *Carcharodontosaurus* and “*Spinosaurus* B” was not actually associated with SGM-Din-1, the *Carcharodontosaurus* skull described in 1996, and shows clear differences with the holotype of *Carcharodontosaurus*. Other features of “*Spinosaurus* B” also clearly differ from *Carcharodontosaurus*, lending support to the notion that it (and therefore *Sigilmassasaurus*) is a separate taxon (Novas et al., 2005).

Albeit research reassigned the *Sigilmassasuarus* remains onto the *Spinosaurus morcoccanus* species, the disputed validity of this species continues. Additionally recent publication and research reassigned the differentiation of the Sigilmassasaurus once more, a unique specimen has recovered.

An unusual mid-cervical vertebra belonging to a large spinosaurid from the Cenomanian Kem Kem Group of Morocco is described. It is compared to the characteristic morphology of each reconstructed cervical position in Spinosaurus aegyptiacus, based on a recent composite reconstruction that incorporates most previously referred material from this unit.

Rather than conforming to any of the previously identified cervical positions in its morphology, the specimen displays a unique combination of mid-cervical characters, with the relatively compact centrum suggesting a position as C4, and the form of the neural arch laminae suggesting a position as C5 or C6. Furthermore, it displays two characters that are previously unknown in spinosaurid mid-cervicals from the Kem Kem Group, directly confirming a highly differentiated theropod.

It also has a rounded hypapophyseal tuberosity that is not continuous with a ventral keel, and a moderately developed, dorsally oriented epipophysis that does not overhang the postzygapophysis posteriorly. The diagnostic value of positionally variable cervical vertebral characters in spinosaurid systematics is discussed. Although limited, the new data could lend support to the controversial hypothesis that two spinosaurid taxa are represented in the Kem Kem Group.

A quadrate bone from the Kem Kem beds was putatively assigned to *Sigilmassasaurus* and it presumably shows the ecological occurrence of two spinosaurid species in Morocco.

## Paleobiology

Several large theropods (more than one tonne) are known from the Cenomanian of northern Africa, raising questions about how such animals would have coexisted. Species of *Spinosaurus*, the largest known theropod, has been found in both morocco and egypt, as has the huge *Carcharodontosaurus*. Two smaller theropods, *Deltadromeus* and *Bahariasaurus*, have also been found in Morocco and Egypt, respectively, and may be closely related or possibly the same genus. *Sigilmassasaurus*, from Morocco, and “*Spinosaurus* B”, from Egypt, represent a fourth type of large predator. This situation resembles that in the Late Jurassic Morrison Formation of North America, which boasts up to five theropod genera over one tonne in weight, as well as several smaller genera (Henderson, 1998; Holtz et al., 2004). The conditions about these species present a similar analogy with today's African Savanna Ecology and Species. (Farlow & Pianka, 2002).

## JPInstitute.com Description

Sigilmassasaurus seems to be a close relative of Spinosaurus. Not very much of this dinosaur has been found, but the bones of its spine, called vertebrae, look very similar to those of Spinosaurus. This was a medium-sized meat-eater that roamed what is now northern Africa. It was originally thought to be another type of Spinosaurus and some scientists think it may be a small Carcharodontosaurus.

Recently, the genus Sigilmassasaurus has been questioned. It is being suggested that the vertebrae belong to a Carcharodontosaurus species. It is also believed that these remains are those referred to by Stromer as Spinosaurus B.

## Links

https://web.archive.org/web/20030324205922/http://www.jpinstitute.com/dinopedia/dinocards/dc\_sigil.html

## References

1. ↑ https://journals.library.ualberta.ca/vamp/index.php/VAMP/article/view/29370
2. ↑ https://journals.library.ualberta.ca/vamp/index.php/VAMP/article/view/29370
3. ↑ https://cdnsciencepub.com/doi/10.1139/cjes-2012-0129
4. ↑ https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0144695