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[dinosaur] Crocodylomorph from Cretaceous Blesa Formation, Spain + Triassic cynodont Massetognathus pectoral limbs

Ben Creisler

New non-dino papers:


J. Parrilla-Bel & J. I. Canudo (2018)
New longirostrine crocodylomorph remains from the Blesa Formation (Barremian) in the Iberian Peninsula (Spain).
Journal of Iberian Geology (advance online publication)
DOI: https://doi.org/10.1007/s41513-017-0043-1


Crocodylomorpha has been a highly morphologically and ecologically diverse clade over time. During the Mesozoic and Cenozoic, several crocodylomorph lineages colonized the marine environment; however, by the late Early Cretaceous the extinction of Thalattosuchia and the origination of new marine forms occur, and the âMiddleâ Cretaceous is a period of time where marine crocodylomorphs are poorly known. Here we describe two rostrum fragments (MPZ 2016/78 and MPZ 2016/79) collected in the upper part of the Blesa Formation (Barremian, Lower Cretaceous) in Teruel (Spain). The âUpperâ Blesa Fm has been interpreted as a coastalâtransitional depositional environment.


The specimens correspond to long-snouted crocodylomorphs. MPZ 2016/78 is the left half of a fragmentary rostrum with heterodonty in dentition size, M4? and M5? being the largest alveoli. This suggests that it belongs to a crocodylomorph with a generalist diet. By contrast, MPZ 2016/79 is a fragmentary right half of a more gracile and slender long rostrum. It is homodont in size, with several small teeth, common in animals specialized for ichthyophagy.


MPZ 2016/78 and MPZ 2016/79 have been assigned to Crocodylomorpha indet. This new crocodylomorph material, together with the fossil remains of marine vertebrates previously found in the same region (plesiosaurs, chelonians, osteichthyans, chondrichthyans and a new crocodylomorph), suggests that the âUpperâ Blesa Formation was a coastal zone with a great wealth of fauna, making it an interesting area for the study of Barremian marine vertebrates.


Phil H. Lai, Andrew A. Biewener and Stephanie E. Pierce (2018)
Three-dimensional mobility and muscle attachments in the pectoral limb of the Triassic cynodont Massetognathus pascuali (Romer, 1967).
Journal of Anatomy (advance online publication)
DOI: 10.1111/joa.12766

The musculoskeletal configuration of the mammalian pectoral limb has been heralded as a key anatomical feature leading to the adaptive radiation of mammals, but limb function in the non-mammaliaform cynodont outgroup remains unresolved. Conflicting reconstructions of abducted and adducted posture are based on mutually incompatible interpretations of ambiguous osteology. We reconstruct the pectoral limb of the Triassic non-mammaliaform cynodont Massetognathus pascuali in three dimensions, by combining skeletal morphology from micro-computed tomography with muscle anatomy from an extended extant phylogenetic bracket. Conservative tests of maximum range of motion suggest a degree of girdle mobility, as well as substantial freedom at the shoulder and the elbow joints. The glenoid fossa supports a neutral pose in which the distal end of the humerus points 45Â posterolaterally from the body wall, intermediate between classically âsprawlingâ and âparasagittalâ limb postures. Massetognathus pascuali is reconstructed as having a near-mammalian complement of shoulder muscles, including an incipient rotator cuff (m. subscapularis, m. infraspinatus, m. supraspinatus, and m. teres minor). Based on close inspection of the morphology of the glenoid fossa, we hypothesize a posture-driven scenario for the evolution of the therian ball-and-socket shoulder joint. The musculoskeletal reconstruction presented here provides the anatomical scaffolding for more detailed examination of locomotor evolution in the precursors to mammals.

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