Thursday, September 11, 2014

Spinosaurus surprise

This is a post to discuss some implications of today's huge Spinosaurus reboot by Ibrahim et al. (2014).

What a cool and unexpected morphology.  Stromer was right about the tiny pelvis all along!  With Sigilmassasaurus and bone taxa G, I and J of Russell (1996) as Spinosaurus, we have so much more data now.  Seems Lapparent (1960) had a lot of Spinosaurus material in his Carcharodontosaurus referred specimens (manual phalanx and pedal ungual from Alrar; manual ungual from Dijoua; pedal ungual from from In Abangarit).  These would have been the first Spinosaurus specimens described after Stromer's work and the destruction of the originals in WWII.

MNNHN specimens of Spinosaurus described as Carcharodontosaurus by Lapparent (1960).  1- Distal manual phalanx from Alrar, Algeria initially misidentified as a metatarsal. 11- Manual ungual from Dijoua, Algeria.  12- pedal ungual from Alrar, Algeria.  From Lapparent (1960).


Also interesting is that Medeiros and Schultz (2002) described two caudals from the Alcantara Formation of Brazil as Sigilmassasaurus.  Now that we know these are spinosaurid, they're probably the first postcrania of Oxalaia

Distal caudal vertebra UFMA 1.10.240 probably referrable to Oxalaia, described by Medeiros and Schultz (2002) as Sigilmassasaurus.  From Medeiros and Schultz (2002).


Finally, with the differences noted by Russell between Kem Kem and Baharija 'Sigilmassasaurus', and those visible between the Kem Kem neotype and Baharija Spinosaurus B, it seems possible the aegyptiacus neotype is not conspecific with the Baharija aegyptiacus holotype.  Awkward.  Interestingly, Russell viewed the Kem Kem form as more derived, and this matches some aspects of Ibrahim et al.'s figure S2 comparison between Spinosaurus B and the neotype- the neotype has a narrower distal femur with more elongate condyles (A below), and flatter pedal unguals (D below).  Was it more adapted to swimming than the Baharija Spinosaurus?

Comparison of Baharija Spinosaurus B (IPHG 1922 X45) in yellow with Kem Kem Spinosaurus aegyptiacus neotype (FSAC-KK 11888) in gray.  After Ibrahim et al. (2014).


References- Lapparent, 1960. Les dinosauriens du "Continental intercalaire" du Sahara central. Memoirs of the Geological Society of France. 88A, 1-57.

Russell, 1996. Isolated dinosaur bones from the Middle Cretaceous of the Tafilalt, Morocco. Bulletin du Muse'um national d'Histoire naturelle. 18, 349-402.

Medeiros and Schultz, 2002. A fauna dinossauriana da Laje do Coringa, Cretáceo médio do Nordeste do Brasil. Arquivos do Museu Nacional. 60(3), 155-162. 

Ibrahim, Sereno, Dal Sasso, Maganuco, Fabbri, Martill, Zouhri, Myhrvold and Iurino, 2014. Semiaquatic adaptations in a giant predatory dinosaur. Science. DOI: 10.1126/science.1258750

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