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Giant Abelisaurs |
August 25 , 2016 by Carnoferox Carnotaurus may no longer be the largest abelisaur. Image courtesy of Wikimedia Commons. For the past few years, rumours of giant abelisaurs have been circulating around the internet. Carnotaurus is currently the largest known abelisaur, at an estimated length of 9 meters. Supposedly, some of these abelisaurs exceeded 10 meters in length. Intrigued, I decided to do some research into these giant abelisaurs; these are my findings. Abbreviations: MUCPv, (Museo Universidad Nacional del Comahue, Paleovertebrados), OLPH (Olphin collection of the Museo Geologico e Paleontologico) PRC.NF (Petroleum Research Centre, Nafusah Region) Ekrixinatosaurus The carnotaurine abelisaur Ekrixinatosaurus novasi was first described by Calvo et al. in 2004. It is known from a single specimen, MUCPv-294, consisting of cranial fragments and a partial postcranial skeleton. It was recovered from the Cenomanian Candeleros Formation of Argentina. Calvo et al. originally estimated a length of 7-8 meters for Ekrixinatosaurus. However, in 2011 Juárez-Valieri et al. proposed a length of 10-11 meters based on skull comparisons with other abelisaurs, notably Carnotaurus. Ekrixinatosaurus has an estimated skull length of 85 cm, compared to 59 cm for the skull of Carnotaurus. Thus, they concluded that Ekrixinatosaurus must be larger. However, in 2013, Novas et al. noted that Juárez-Valieri et al. had overlooked the fact that Ekrixinatosaurus has a shorter femur length (77 cm) than Carnotaurus (103 cm). The skull-to-femur ratio of Ekrixinatosaurus is 1.08, whereas in Carnotaurus it is 0.58. This means that proportionate to Carnotaurus, Ekrixinatosaurus was smaller but had a larger head. The original estimate for the length of Ekrixinatosaurus (7-8 meters) was thus reinstated by Novas et al.“Titanovenator“ “Titanovenator kenyanensis“, as it has been unofficially dubbed, has so far only been featured in a brief abstract by Sertich et al. that was presented at the 73rd annual meeting of the Society of Vertebrate Paleontology in 2013. According to the abstract, “Titanovenator” is known from fragmentary cranial and postcranial remains. These fossils have been recovered from the Maastrichtian Lapurr (alternatively spelled Lapur or Lubur) Sandstone of Kenya. Sertich et al. claimed a 11-12 meter estimate for “Titanovenator”, which would make it by far the largest abelisaur ever discovered. Unfortunately, they fail to describe exactly how these estimates were reached. The limited information on “Titanovenator” makes such large size calculations dubious. Until a full analysis of the material is published, “Titanovenator” will remain an indeterminate abelisaurid.“Errachidiasaurus” (OLPH 025) Specimen OLPH 025 was recently described in a 2016 paper by Chiarenza and Cau. This indeterminate abelisaurid is known from a partially preserved femur recovered from the Cenomanian Kem Kem Compound Assemblage of Morocco. I have informally named it “Errachidiasaurus giganteus”, after Errachidia, the province where it was found. Chiarenza and Cau calculated a total length of between 77 and 92 cm for the femur (compared to 103 cm for Carnotaurus). However, they noted that the femur may have been as long as 120 cm, depending on if “Errachidiasaurus” belonged to the gracile or robust morphotypes present in abelisaurs. Based on the size of the femur, they estimated lengths of up to 9 meters for “Errachidiasaurus”. This estimate means that it could rival Carnotaurus in size, potentially making it the largest abelisaur. “Libyacolossus” (PRC.NF.1.21) PRC.NF.1.21, an indeterminate abelisauroid, was first described in 2010 in a paper by Smith et al. It is known from associated postcranial remains from the Aptian Cabao Formation of Libya. I have given PRC.NF.1.21 the moniker of “Libyacolossus ingens”. Smith et al. estimated that the femur of “Libyacolossus” was between 80 and 100 cm long, comparable to other large abelisaurs. Once again, the femoral length could vary depending on if it was gracile or robust. Based on the femoral estimates, they calculated a total body length of 7-9 meters for “Libyacolossus”. If it was in the upper size range, “Libyacolossus” could be another potential candidate for the largest abelisaur.Conclusion It appears that the rumours of abelisaurs exceeding 10 meters are untrue. Ekrixinatosaurus was only 7-8 meters, oversized due to faulty calculations. “Titanovenator” is unpublished, dubious, and likely overestimated. However, “Errachidiasaurus” and “Libyacolossus” may have reached 9 meters, making them contenders for the largest abelisaur. For now, 9 meters seems to be the maximum size for an abelisaur. References:
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