| Acostasaurus | |
|---|---|
 | |
| Cranial reconstruction ofAcostasaurus pavachoquensis | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | †Sauropterygia |
| Order: | †Plesiosauria |
| Suborder: | †Pliosauroidea |
| Family: | †Pliosauridae |
| Genus: | †Acostasaurus |
| Species: | †A. pavachoquensis |
| Binomial name | |
| †Acostasaurus pavachoquensis Gómez Pérez & Noè,2017 | |
Acostasaurus (meaning "Acosta's lizard") is an extinct genus of possiblyThalassophoneanpliosaurid known from theBarremian of thePaja Formation,Colombia. The type specimen,UNDG R-1000, is known from a near complete skull, and postcranial elements including a complete hindlimb and various vertebrae.[1] The specimen has an estimated size of over 4 metres (13 ft) in length.[2]
The type specimen is noted for possessing several features that pertain to a subadult individual: for example, the sagittal crest is not fully ossified, as well as possessing undeveloped palatine wings. It is possible however thatAcostasaurus, like otherplesiosaurs, waspaedomorphic.[3]
From what is preserved, the orbits are large, rounded and deeply notched dorsally. The sclerotic ring of the specimen is also very large, suggesting thatAcostasaurus was adapted to see in deep or murky waters.
An unusual feature ofAcostasaurus is that it possesses a short mandibular symphysis, containing only 6 pairs of functional alveoli (5 and ½, considering that the symphysis terminates level with the middle of the sixth pair). The short, wide symphysis is one of the features which differentiatesAcostasaurus from other contemporary pliosaurids such as the variousbrachauchenine pliosaurs from the formation.[1] Other pliosaurids which possess this condition include theJurassic taxonSimolestes, which likeAcostasaururs has large orbits, as well as a short symphysis.[4] Gómez-Pérez et al. note that the base of the functional alveoli inAcostasaurus are confluent with Meckel's canal as inSimolestes, and that it also possessed a heavily swollen and ornamentedsagittal crest to form a parietal knob, also found inSimolestes.[1]
As brachauchenine pliosaurs are the only pliosaurids known from the Barremian stage, especially from Colombia, Gómez Pérez et al. comparedAcostasaurus to a variety of brachauchenine taxa in the paper. The authors however concluded that referral of the genus to the subfamily is problematic:Acostasaurus possessescaniniform dentition, whereas brachauchenines possess longirostrine homodont dentition. As discussed before,Simolestes and other less derived pliosaurids possess similar dentition, especially in the arrangement that are present inAcostasaurus.[1]
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