The proximodorsal
process
A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic.
Things called a process include:
Business and management
*Business process, activities that produce a specific se ...
is a feature of the skeleton of
archosaur
Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avi ...
s. It may be a pair of tabs or blade - shaped flanges on the pelvis, and serves as an anchor point for the attachment of leg muscles. This process is of particular importance in the
anatomy
Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...
and
comparative morphology
Comparative anatomy is the study of similarities and differences in the anatomy of different species. It is closely related to evolutionary biology and phylogeny (the evolution of species).
The science began in the classical era, continuing in t ...
of
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Creta ...
birds and advanced
maniraptora
Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the non-avian dinosaurs that were more closely related to them than to '' Ornithomimus velox''. It contains the major subgroups Avialae, Deinonychosauria, Ovirapt ...
n
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s. The
pelvis is made up of three paired bones and a
sacrum
The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30.
The sacrum situates at the upper, back part ...
. The three paired bones are called the
ilium
Ilium or Ileum may refer to:
Places and jurisdictions
* Ilion (Asia Minor), former name of Troy
* Ilium (Epirus), an ancient city in Epirus, Greece
* Ilium, ancient name of Cestria (Epirus), an ancient city in Epirus, Greece
* Ilium Building, a ...
, the
, and the
pubis. On the
there may be an
obturator process The obturator process is an anatomical feature on the pelvis of archosaurs.
It is a raised area of the ischium bone of the pelvis.Romer, Alfred S. (1923) "The Pelvic Musculature of Saurischian Dinosaurs" "Bulletin of the American Museum of Natural ...
and/or a proximodorsal process. The more
primitive
Primitive may refer to:
Mathematics
* Primitive element (field theory)
* Primitive element (finite field)
* Primitive cell (crystallography)
* Primitive notion, axiomatic systems
* Primitive polynomial (disambiguation), one of two concepts
* Pr ...
condition is for there to be no proximodorsal process, but a large
obturator process The obturator process is an anatomical feature on the pelvis of archosaurs.
It is a raised area of the ischium bone of the pelvis.Romer, Alfred S. (1923) "The Pelvic Musculature of Saurischian Dinosaurs" "Bulletin of the American Museum of Natural ...
. In primitive birds the ischia are complex, usually with a small or even absent obturator process and a large, rectangular, proximodorsal process extending up toward the ilium. This is the condition in ''
Archaeopteryx
''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...
'',
Confuciusornis
''Confuciusornis'' is a genus of basal crow-sized avialan from the Early Cretaceous Period of the Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago. Like modern birds, ''Confuciusornis'' had a toothless beak, b ...
, and
enantiornithines.
[ Witmer, Lawrence M. (2002) "The Debate on Avian Ancestry: Phylogeny, Function, and Fossils." pp. 3-30 in "Mesozoic Birds: above the heads of dinosaurs" Chiappe, L.M., and Witmer, L.M. (eds.) University of California Press, Berkeley.] The South American
dromaeosaur
Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...
s called the
unenlagiinae have an intermediate condition
[Forster, Catherine, Sampson, Scott D., Chiappe, Luis M., Krause, David W. (1998) "The Theropod Ancestry of Birds:New Evidence from the Late Cretaceous of Madagascar" "Nature" 279:1915-1919. 20 march 1998] between the two, with both a large obturator process and a proximodorsal process.
[ Makovicky, Peter J., Apestguia, Sebastian, Agnolin, Frederico L. (2005) "The earliest dromaeosaurid theropod from South America" "Nature" 437:1007-1011 13 October 2005.]
See also
*
Epipubic bones
*
Evolution of mammals
The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the Pennsylvanian (geology), Pennsylvanian sub-period of the late Carboniferous period. By the mid-Triassic, there were many synaps ...
References
{{wikt
Dinosaur anatomy
Mesozoic birds
Mesozoic dinosaurs