development of osteoderms and queratinization (modified from Alibardi,
L. & Thompson, M.B. 2000)
dinosaurs. Recently, some eggs bearing titanosaur embryos with preserved skin, from Patagonia, Argentina, may shed
some light on the function and disposition pattern of these dermic bones. Some of the skin patches associated with the
titanosaur embryos show two distinct patterns of tuberosities: a longitudinal row and rosettes, both composed of closely
attached tuberosities. These tuberosities do not seem to be ossified, but this might be due to the ontogenetic stage of
the titanosaurs. Here is proposed that these tuberosities might have been ossified in later ontogenetic stages, and then
turning into real osteoderms providing physical defense for the juvenile titanosaurs.
Peirópolis, Uberaba, Minas Gerais. On the right: fossil
embryo´s skin patches from Patagonia, Argentina
(modified from Chiappe et al. 1998). Arrows point to
hypothetical placement of adult osteoderms on embryo´s
pattern.
small to the animals when compared to other dinosaurs and
crocodyliforms. These bones would not provide real defensive
advantage to an adult titanosaur as they are small and also have
a very spongy internal structure. This apparent fragility also may
be the reason that few titanosaur osteoderms have been
preserved.
osteoderm and its body armor would be
much more effective against small predators
like notosuchian crocodyliforms and small
theropods. And if the titanosaur osteoderms
are originated from the embryo's
tuberosities, the disposition of these
elements in an adult animal would be very
distant to each other. Therefore, the function
of osteoderms in adult titanosaurs would
have been of calcium reserve rather
defensing.
(Drawings by Deverson da Silva "Pepi")
Dr. Ismar de Souza Carvalho (Instituto de Geociências,
Universidade Federal do Rio de Janeiro), Luiz Carlos Borges
Ribeiro (Centro de Pesquisas Paleontológicas Llewellyn Ivor Price),
Dr. Luis Chiappe (Vertebrate Paleontology, Natural History Museum
of Los Angeles County) and Dr. Ralph Molnar (Museum of Northern
Arizona) for their kind assistance and encouragement. Coordenação
de Aperfeiçoamento de Pessoal de Nível Superior (CAPES),
Instituto Virtual de Paleontologia da Fundação Carlos Chagas Filho
de Amparo à Pesquisa do Estado do Rio de Janeiro (IVP/FAPERJ)
supported this study.