synsacrum

The last few are fused with the pelvis to form the synsacrum.

A related skeletal structure, found mainly in birds and dinosaurs, is the synsacrum.

In terms of external morphology, the synsacrum corresponds to the rump.

A second partial synsacrum similar to the type specimen had been described in 1995, and may also belong to Gargantuavis.

It is known from a single fossil specimen: a synsacrum, the fused series of vertebrae over the hips.

The innominate bones are fused with the synsacrum to a greater or lesser extent, according to species, forming an avian pelvis.

Mallon presumed that the synsacrum, the fused vertebrae supporting the pelvis, had shifted to the rear.

The central section of the synsacrum is swollen to accommodate the glycogen body, an organ whose function is as yet unclear but which may be associated with balance.

Posterior to the synsacrum there are a few free caudal vertebrae, the last of which is the pygostyle to which the long, stiff tail feathers are attached.

A Pelvic skeleton including a synsacrum, was recovered from mudstone in the Linxia Basin, Guanghe County, Gansu Province, northwest China.

The synsacrum is a skeletal structure of birds and dinosaurs, in which the sacrum is extended by incorporation of additional fused or partially fused caudal or lumbar vertebrae.

The synsacrum is a similar fused structure found in birds that is composed of the sacral, lumbar, and some of the thoracic and caudal vertebra, as well as the pelvic girdle.

The sacral vertebrae are fused with the lumbar vertebrae, and some thoracic and caudal vertebrae, to form a single structure, the synsacrum, which is thus of greater relative length than the sacrum of mammals.

In 2007 S. Christopher Bennett claimed that the holotype and the referred material came from different forms and that, while the last was indeed of a pterodactyloid nature, the synsacrum belonged to a member of the Anurognathidae.

Like with other ankylosaurians, the last four dorsal vertebrae and the first caudal vertebra are thus fused to the sacrum, forming a reinforced synsacrum of at least eight vertebrae, the spines of which form a fused supraneural plate, also incorporating the zygapophyses.

A list of synapomorphies convergent with Ornithurae observed in Ceratosauria includes such quintessential traits as: a) synsacrum present, b) pubis, ilium, ischium fused, c) astragalus and calcaneum fused, and confluent with tibia, d) tarsometatarsus present.

The holotype is BYU 2024, a synsacrum of seven sacral vertebrae, featuring a unique - for a pterosaur - complete fusion of the spinae into a supraneural blade, a character, as the specific name indicates more typical for birds, at first leading Jensen to assign the fossil to a bird, Paleopteryx.