Objetos perdidos y encontrados de Suchosaurus girardi en las VI Jornadas de Salas de los Infantes

Las colecciones científicas de los grandes museos de historia natural nunca dejan indiferente a nadie. Buscando en el bául de los recuerdos del Museu Nacional de História Natural e da Ciência (MUHNAC) de Lisboa encontramos un "objeto" perdido en el siglo pasado, parte del holotipo de Suchosaurus girardi (Sauvage, 1897-98). Este hallazgo museográfico fue presentando en formato póster en las VI Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno de Salas de los Infantes (Burgos).

Aquí os dejamos el resumen:

The species of crocodile Suchosaurus girardi (Sauvage, 1897-98) was based on two jaw fragments with teeth and an isolated tooth collected at the locality of Boca do Chapim (Sesimbra, Portugal). The specimen was later reinterpreted and referred to the spinosaurid dinosaur Baryonyx. This last work was based on the redescription of the jaw fragments (MG324, which includes the two fragments reported by Sauvage, 1897-98 and a third unpublished jaw fragment) deposited on the collections of the Museu Geológico (Lisbon) but the isolated tooth could not be located by the author and was considered lost. However, during recent researches on the collections of paleontology of the Museu Nacional de História Natural e da Ciência (MUHNAC) we found this tooth (MNHN/UL.I.F2.176) among some of the material that was rescued of the fire that destroyed much of the museum on 1978. There are also other specimens from the same locality, such as a tooth assigned to the theropod Megalosaurus aff. superbus beside some labels of material that we have not been able to locate so far. These fossils were collected by P. Choffat during their researches for the service of the Direcção dos Trabalhos Geológicos de Portugal (Direction of Geological Works of Portugal). The geological surveys carried by the DGT (later named Serviços Geológicos) as well as the study of the thousands of geological and paleontological samples collected during these works were apparently developed in collaboration with researches of the MUHNAC.
The Boca do Chapim locality is one of the few sources of Early Cretaceous tetrapod remains from the Lusitanian Basin. The fossils described by Sauvage come from sediments of the Papo Seco Formation, which is considered early Barremian in age. The vertebrate assemblage known at the moment from this locality consists of remains identified to fishes, chelonians and dinosaurs, including ornithopods, sauropods and theropods.
The specimen herein referred corresponds to a tooth crown without its apex. It measures 30mm on maximum length from the most apical end to the base. The crown presents a conical outline, only weakly labiolingually compressed, and with a slightly recurved distal end. The specimen is well preserved but on one face all the enamel surface is missing. On the surface that preserves the enamel it is possible to verify the presence of at least 5 vertical ridges. These well-define parallel flutes extend along the entire preserved surface from the apical tip to the base. Beside these ridges the enamel presents also a particular ornamentation consisting on a series of thin crenulations, which gives a rough aspect to the crown. The distal carina is missing due to fracture and the mesial one is almost entirely covered with sediment so the presence of denticles could not be verified. The cross-section at the base of the crown is oval in outline, with the long axis mediodistally oriented; it measures 14mm on mediodistal length and 9mm on labiolingual width.
The material previously assigned to Suchosaurus girardi by Sauvage was reinterpreted as Baryonyx based on the recognition of a combination of characters share with Baryonyx walkeri from the Barremian of England. The specimen MNHN/UL.I.F2.176 presents a general morphology very similar to the teeth on the jaw fragments described by Buffetaut and some of the characters considered synapomorphies for baryonychine spinosaurids (e.g. the conical shape of the crown with well-marked vertical ridges and distinctive ornamentation of the enamel). Most of the theropod teeth present crowns very compressed labiolingually and smooth enamel surfaces. Only spinosaurid theropods present enamel ornamentation with well-defined vertical ridges and thin crenulations. The teeth from Boca do Chapim differs from those of Baryonyx walkeri in the presence of ribs on both sides of the crown whereas the teeth of the holotype usually have smooth labial surfaces. Other baryonychine teeth from England present ridges on both lingual and labial surfaces; and this morphology is also present on some teeth from Spain. The specimens from Boca do Chapim are also similar to some teeth from the Late Jurassic of Tendaguru Formation (Tanzania) on the presence of several longitudinal ridges on both sides and a fine wrinkling on the enamel. Based on these characters Buffetaut suggested that these teeth might represent an early spinosaurid. Although, the fine wrinkling of the enamel on the Tendaguru specimens is weakly developed unlike the granular texture in the Portuguese specimens and in other baryonychines.
More recently, other specimen consisting on cranial and postcranial material from Praia das Aguncheiras, about 15km to the southeast of Boca do Chapim, was also assigned to the species Baryonyx walkeri. This specimen comes from Barremian sediments of the Papo Seco Formation that correspond to the same levels as the fossils described by Sauvage.
The record of baryonychine spinosaurids known at the moment suggests that these were common on the theropod assemblages from the Early Cretaceous of Europe. The group is represented on sediments of the Hauterivian, Barremian and Aptian from England, Portugal and Spain. Some authors argued that the presence of baryonychines in the Iberian Peninsula may be of some paleobiogeographic importance to explain the dispersion of this group of dinosaurs between Europe and Africa, which may have taken place via a route thought Iberia.

Mas información:

  • Imagen: En la foto superior, Elisabete Malafaia y Francisco Ortega buscando fósiles perdidos por ahí. En la foto inferior, el poster presentado en las Jornadas.

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