Big Sara

Credit: Darren Naish.

Big Sara is an unnamed genus of allosauroid that lived in Wyoming during the Late Jurassic.

## History

—Darren Naish
The genuine specimen was placed on display in 2022 at the Westquay Shopping Centre food court as tie-in marketing for *Jurassic World: Dominion*, which released that same year. Darren Naish visited the specimen, noting that the air conditioned space would not have advanced decay, with the weather of the United Kingdom not being humid and the specimen standing in an open space near a window. He is not sure if these conditions are contributing to pyrite decay. It was described by Godefroit as a new allosauroid taxon. The specimen was discovered in 2015 on a steep hill in the Morrison Formation, taking two years to fully remove before being prepared and the missing remains were cast and reproduced with resin for display in the shopping mall to excite visitors.

## Description

Big Sara contains synapomorphies that are characteristic of Allosauroids and others that are unusual for *Allosaurus*, which suggest that it may belong to an unnamed genus. The dentary is elongate and more slender than *Allosaurus*, closer resembling *Marshosaurus*. The caudal of the dentary is thin and dorsoventrally expanded, with height terminating rostrally along the caudal third (which is concave, remaining straight rostrally as in *Allosaurus* but nor *Marshosaurus*). It curves up in the rostral half, with the mandibular symphasis being flat and forming a flattened surface that inclines rostrolaterally. It is pierced by a series of neurovascular foramina 2 centimeters below the dorsal margin and generally correspond with the alveolus. There are 18-19 of the latter in the complete tooth row. In the dorsal, the dentary is nearly straight and not as laterally bowed as in *Allosaurus*. The angular is elongate and curves ventrally to form the caudal of the ventral margin of the mandible. It is more slender than *Allosaurus*, especially in the lateral (making less than 1/4 of the total caudal aspect height). The articular is forced between the surangular and the prearticular rostrally. The articular and surangular contribute to form the lateral glenoid fossa like *Allosaurus* to the dorsoventral. The medial glenoid fossa is narrower, deeper and forms the retroarticular process by a high, sharp ridge. The retroarticular process is more robust than *Allosaurus* and is cadually-directed. A prominent articular is also seen in *Allosaurus* and *Bagaraatan* and present between the articular, prearticular and surrangular, possibly to prevent caudal disarticulation in the jaw joint. It is more prominent than *Allosaurus*. The articular forms a sharp, high sinuous ridge between the antarticular and retroarticular process, which is unique to the genus, This and the median of the articular medially expand to form the wide medial shelf, with a dorsal surface that is deeply excavated and has a foramen that enters the rostroventral wall. This opening presumably carried a diverticulum of the tympanic air sac into the hollow articular core.

There are four premaxillary teeth on each side of the skull, which is less than *Allosaurus* and more than *Torvosaurus* and *Ceratosaurus*. However, the premaxilla-maxilla contact is poorly preserved so the tooth count reaching 5 (as in *Allosaurus*) can not be ruled out. The maxillary-dentary teeth size difference is striking and carries heavier taxonomic weight compared to other allosauroids. The carinae in the maxillary-dentary teeth are symmetrical along the main tooth axis, although they are slightly medially offset as in *Allosaurus* and *Acrocanthosaurus*. The vertebral pleurocoels are less clearly developed on the cervicals and anterior dorsals than in Allosaurus, which Godefroit notes must be verified after preparation is complete. The spinous and transverse processes are prominent, like *Allosaurus*. The elongate scapula, 86% of the femoral length, is slender compared to *Allosaurus* and *Ceratosaurus*, regularly curving in the ventral and dorsal to follow the ribcage profile. The acromial process is more sharply expanded from the craniodorsal margin of the blade than *Allosaurus* and *Sinraptor*. The glenoid sharply demarks from the rostroventral margin of the blade. The coracoid facet and glenoid are subequal in size and forms an angle of 115°. The dorsal border is straight in the caudal and the dorsal third of the scapula expands ventrally. The distal portion of the blade is more expanded than *Allosaurus* and *Ceratosaurus*. The pubis is more robust than *Allosaurus*, with the fusion between the pubes being more extensive than the latter as well. The distal boot is cranially expanded, forming an angle with the pubic shaft and the causal is more dorsally inclined than *Allosaurus*.

## Paleobiology

Naish also examined the anatomy of the specimen. He finds that the nasals are some of the most complex he has observed in "*Allosaurus*" (which this specimen may not belong), clusters of hornlets (which he notes may be the result of human sculpting) at the antorbital fenestra and serrated lacrimal edges. The latter, appearing anatomically valid and part of the real specimen, would have been enlarged by keratin in life, creating a grandiose display. Mark Witton disagrees, that the serrated edges are typical in keratin support. The specimen is considered property of the Richmond Group, which indicates uncertainty for the whereabouts of Big Sara henceforth.

## References

* https://twitter.com/TetZoo/status/1538286000631386112
* https://twitter.com/MarkWitton/status/1538817002990714880
* https://twitter.com/TetZoo/status/1538634401457786880
* https://www.gazette-drouot.com/telechargement/catalogue?venteId=91035
* https://www.dorsetbiznews.co.uk/dino-mite-millions-to-see-big-sara-dinosaur-fossil-at-westquay-thanks-to-dorset-company/