INVESTIGADORES
EZCURRA Martin Daniel
congresos y reuniones científicas
Título:
Preliminary analysis of macroevolutionary patterns in the variation of cranial morphotypes in the proterochampsid archosauriforms from the Triassic of South America
Autor/es:
TROTTEYN, M. J.; EZCURRA, M. D.
Lugar:
Buenos Aires
Reunión:
Jornada; XXVI Jornadas Argentinas de Paleontologia de Vertebrados; 2012
Resumen:
Proterochampsids are Triassic archosauriforms documented from the well-sampled Los Chañares (Ladinian) and Ischigualasto (Carnian?Norian) formations of Argentina and coeval levels of the Santa María Formation of Brazil. The anatomy and phylogenetic relationshipsof proterochampsids have been studied in detail, but the macroevolutionary patterns within the group have been mostlyignored. Thus, our aim was to analyse variations observed in proterochampsid cranial morphological diversity through time in orderto characterize some aspects of their macroevolutionary history. Three cranial morphotypes were recognized qualitatively, which mayrepresent different ecomorphotypes: 1) strongly dorsoventrally compressed skulls (Chanaresuchus Romer, Proterochampsa Reig); 2)dorsoventrally tall skulls (Gualosuchus Romer); and 3) moderately compressed skulls (Cerritosaurus Barberena, Rhadinosuchus Huene,Tropidosuchus Arcucci). The apex of morphological diversity is observed in the Los Chañares Formation with the presence of all threemorphotypes, whereas in the Ischigualasto Formation the diversity is restricted to morphotype 1 only. By contrast, morphotypes 1and 3 are both recorded in the Brazilian beds coeval to the Los Chañares (Dinodontosaurus AZ) and Ischigualasto (HyperodapedonAZ) formations. Accordingly, a decrease in cranial morphological diversity is observed in the Argentinean basin during the Carnian?Norian relative to the Ladinian, but morphological diversity is constant through time in the Brazilian basin. These patternsmay reflect different macroevolutionary histories occurring in the two basins, in particular the probable extinction of morphotypes2 and 3 in the Late Triassic of Argentina. The hypotheses proposed here will be tested in the future with the continuously improvedsampling of the South American Triassic beds.