IDEAN 23403
INSTITUTO DE ESTUDIOS ANDINOS "DON PABLO GROEBER"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
A spectacularly preserved Early Permian dvinosaur (Temnospondyli) from the Parnaíba Basin (Brazil) illuminates the anatomy , functional morphology, and evolution of aquatic locomotion in the clade
Autor/es:
MARSICANO, CLAUDIA; ANGIELCZYK, KEN; CISNEROS, JUAN
Lugar:
Berlin
Reunión:
Congreso; 74th Annual Meeting of the Society of Vertebrate Paleontology; 2014
Resumen:
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Since
2011, fieldwork has been conducted in the Early Permian Pedra de Fogo Formation
(PFF) of the Parnaíba Basin to study its age, depositional environments, and
vertebrate faunas. Discoveries include several articulated skeletons of a new
temnospondyl. Phylogenetic analysis indicates that the species is a basal
dvinosaur. The Brazilian dvinosaur has a well-ossified skeleton, and is
characterized by a large head and ceratobranchials, a robust pectoral girdle,
rhachitomous vertebrae with a large notochordal space, and caudal vertebrae and
ribs that are modified into a rigid fin-like structure. Small limbs are
present, and include ossified stylopodial, zeugopodial, and autopodial
elements. The Brazilian species shares an elongate body plan with the Permian
and Early Triassic tupilakosaurids, but the structure of the vertebrae differs.
The short, disc-like diplospondylous centra of tupilakosaurids resemble the
centra of taxa such as whales and ichthyosaurs, which have inflexible vertebral
columns. In contrast the vertebrae of the Brazilian species are more elongate
and consist of a ring of bone that surrounded the notochord. We interpret this
morphology as indicative of a highly flexible vertebral column. Together, these
characters suggest a fully aquatic animal that was well adapted to anguilliform
swimming. The large head may have been used in combination with powerful body
movements for penetrating dense aquatic vegetation, but the limbs were better
suited to fine movements and position holding. The phylogenetic placement of
the new taxon implies that this general bauplan evolved before the origin of
tupilakosaurids; further refinement within the clade included the evolution of
a more rigid vertebral column. The PFF dvinosaur is a member of a complex
lacustrine ecosystem characterized by several guilds of aquatic secondary
consumers, and at least some localities seem to preserve mass death assemblages
of the species. The PFF samples a previously unknown biogeographic province in
western tropical Gondwana, and other members of the lacustrine community
include a new trimerorhachid and the oldest and northernmost occurrence of a
rhinesuchid.
