Researchers believe the creature is a "stem amniote
" _ a likely ancestor of several groups of land-dwelling animals that later differentiated into modern mammals, birds and reptiles.
Compared with anamniotes, the amniotes
have fewer commissures during initial development although the amniotes
eventually form these but at later stages.
Finally, tetrapod remains from amniotes
were recovered from the Balearic Islands, including cranial and postcranial material (Cala Pilar, Menorca Island) (13) (Pretus and Obrador, 1987), being nowadays under preparation and study.
Triacylglycerols (TAG), the principal yolk lipid in oviparous amniotes
, are the main source of metabolic energy during development and following hatching during a nutritional stage termed postnatal lecithotrophy (Lance and Morafka, 2001).
This is not to say that comparative immunology has been absent or unimportant; it has always been a center of interest among both immunologists and evolutionary biologists, and comparative studies within amniotes
underlie key concepts such as that of immune tolerance (Owen, 1945) and critical functional distinctions such as that between B-and T-lymphocytes (Cooper et al., 1966).
The origin and early evolutionary history of amniotes
. Trends in Ecology and Evolution, 12, pp.
But if the amniotes
are considered, Australia has the highest number of these species under threat among all developed nations (IUCN, 2004b).
It covers gametogenesis and fertilization, lineage tracking, oogenesis and other early development, development in amphibians and amniotes
, vertebrate organogenesis including metamorphosis, plant development, morphogenesis, regulations of gene expression, and evolution.
Our evolutionary roots--the amniota-began a great divergence when a few amniotes
crawled out of a primordial sea and left their finned relatives behind.
The human embryonic circulatory system is a modification of that used in other amniotes
, such as birds and reptiles.
To illustrate the breadth of his curiosity-driven insight, consider the following titles of papers he published with co-authors: i) The spiral in the tusk of the narwhal (1988, Arctic 41:236-238); ii) Constraints on brain growth (1989, Nature 340:194); iii) The evolution of viviparity in amniotes
: egg retention vs.
They have long believed two groups of animals - amphibians and amniotes
- evolved from common ancestors hundreds of millions of years ago.