Putative latest Cretaceous carcharodontosaurs
Carcharodontosaurs reached their acme in the middle Cretaceous, from Aptian to Cenomanian. In recent years, some researchers have claimed they survived in South America well past that time. On the basis of discoveries in Campanian and Maastrichtian strata, carchs are said to have survived to the latest Cretaceous or K-Pg. I don't believe the evidence is sufficient, however. Even if the material is undoubtedly carcharodontosaurid, it is extremely limited and fragmentary, which suggests reworking.
Based on just a single isolated tooth, Martinelli et al. (2004) conclude carcharodontosaurs are present in the Campanian-Maastrichtian Allen formation. How can they be sure the tooth isn't from a Giganotosaurus or Mapusaurus, later reworked into the geologically younger Allen?
Simbras et. al. (2013) are equally incautious. They note the discovery of a partial carch maxilla (below) in the Presidente Prudente formation, also of Campanian-Maastrichtian age. It is considered to indicate the presence of carchs in that unit and time. But again there is just a single isolated element, a mere fragment. If carcharodontosaurs were really present in the latest Cretaceous, why isn't there better material, comparable to that of Carnotaurus?
Perhaps the authors are right and better material will be found, confirming their view. But until it is found I'll consider Schaochilong, of Turonian age, the last of the carchs.
References
Martinelli et al. Late Cretaceous Vertebrates from the Bajo de Santa Rosa (Allen formation) Negro province, Argentina with the description of a new sauropod dinosaur. Revista del Museo Argentino Ciencias Naturales n.s. 6(2) 2004
Simbras et al. First Brazilian carcharodontosaurid and other new therapy finds from theCampanian-Maastrichtian Presidente Prudente formation from Sao Paulo state southeastern Brazil. Cretaceous Research 2013
posted by starman at 5:31 AM
4 Comments:
I personally consider that evidence to be insufficient. More teeth and some postcranial remains are necessary to make a solid case for late Cretaceous carcharodontosaurs.
To prove their case the South American researchers need at least few articulated or associated carch elements, instead of just isolated ones.
April 17, 2020
I honestly wouldn´t be surprised if carchs had survived until the latest Cretaceous; titanosaurs and abelisaurs did, after all. One has to remember for example that only one single Carnotaurus specimen has been found (IIRC); I don´t know if isolated Carnotaurus teeth have been found in the same formations, but it would've been just as easy for paleontologists to find only the teeth and wonder what sort of animal it was, and never luck upon the actual skeleton. Paleontologists may have conceivably walked by and missed a latest Cretaceous carch skeleton more than once :B
It is true that carchs and abelisaurs coexisted for some time in the EK and mid-K, so a latest K carch wouldn't be shocking. Yet the lack of conclusive proof in ANY geological unit, anywhere, post Turonian may say something. I note carchs coexisted with tyrannosauroids in the late EK of Asia but the former appear extirpated in Asia post Turonian.
April 18, 2020
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