These warm, shallow seas were not only good for making limestone, but also for preserving the organisms that lived in these seas. A median row of erective spines frill extends from the top of the head to the tip of the tail, but is interrupted at the neck region Fig. Body mass of horse species over time; click for larger; after MacFadden Estuarine or Salt water Crocodile, C. The genus, Osteolaemus, is found in Western Africa and is characterised by having undivided nasal aperture and the snout turned up in front. In practice, some reptiles live in a stable environment and have a stable body temperature. Each hump has a radiating yellow streaks.
A few selected transitional fossils
Typhlopidae vestiges of pelvic bones are present. The chorion and amnion are a fluid filled sac-like structures where development of the embryos proceeds easily in the absence of pond. Thus, reptiles were defined as the set of animals that includes crocodiles , alligators , tuatara, lizards , snakes , amphisbaenians , and turtles , grouped together as the class Reptilia Latin repere, "to creep". Figure 13 --View of the Ordovician trilobite Isotelus , showing the basic divisions of the carapace, or external skeleton adapted from Morphology of the Exoskeleton; in , Treatise on Invertebrate Paleontology, Arthropoda Trilobita, Revised, by H. Black coloured head with light coloured streaks. Mullerian duct persists as oviduct in female and Wolffian duct is retained as vas deferens in male.
Reptiles: Origin, History and Classification
Dinosaurs laid their eggs in nests, and many kinds of dinosaurs then abandoned their eggs to hatch untended, leaving the hatchlings to fend for themselves, much as a turtle does today. Bivalve fossils first appear in rocks that date to the middle of the Cambrian Period, about million years ago. The state's museums are a great place to view spectacular specimens and learn more about all kinds of fossils from Kansas and elsewhere. The reptiles as defined are clearly not monophyletic but rather are paraphyletic , since they exclude both birds and mammals, although these also are considered to be descendant from the original reptile. Palaeontological history started from Triassic about million years ago, but undoubtedly must have originated even earlier in Permian from cotylosaurian ancestors. Living diapsids are extremely diverse, and are considered to include all birds , crocodiles, lizards, snakes, and tuataras and possibly even turtles. The ankle bone in dinosaurs was firmly attached to the shin bones, and this simple hinge construction allowed for a much stronger joint.
It can also monitor the intensity of solar radiation. This is made possible by a muscular ridge that subdivides the ventricle during ventricular diastole and completely divides it during ventricular systole. Before courtship the jaw slap or head slap of the males attracts the female, and the female responds with her own jaw slap. Creatures like them were recorded in the late Triassic, so they are of the slowest rates of evolution. The length of the body is above cm. Some reptiles also present threats to people, whether because they are venomous, like some snakes, or can attack humans, such as some crocodilians.