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Game board with initial setup for Indigo, a modern (2012) game. Early game boards came in a variety of shapes (for example, senet's game board was made of three parallel rows, while mehen's was based on a spiral form); a quadrilateral (square) shape with grids became common only later, with the emergence of strategy games. [6]
The evolutionary split between placentals and marsupials occurred 125-160 million years ago, in the Middle Jurassic-Early Cretaceous period. Presently, close to 70% of the 334 extant marsupial species are concentrated on the Australian continent, including mainland Australia, Tasmania, New Guinea, and nearby islands.
For instance, descendants of the first reptiles include modern reptiles, mammals and birds; the agnathans have given rise to the jawed vertebrates; the bony fishes have given rise to the land vertebrates; a group of amphibians, the labyrinthodonts, have given rise to the reptiles (traditionally including the mammal-like synapsids), which in ...
While the early amniotes resembled their amphibian ancestors in many respects, a key difference was the lack of an otic notch at the back margin of the skull roof. In their ancestors, this notch held a spiracle , an unnecessary structure in an animal without an aquatic larval stage. [ 25 ]
Comparative anatomy is the study of similarities and differences in the anatomy of different species. It is closely related to evolutionary biology and phylogeny [ 1 ] (the evolution of species). The science began in the classical era , continuing in the early modern period with work by Pierre Belon who noted the similarities of the skeletons ...
Primates have a longer juvenile period between weaning and sexual maturity than other mammals of similar size. [57] Some primates such as galagos and New World monkeys use tree-holes for nesting, and park juveniles in leafy patches while foraging. Other primates follow a strategy of "riding", i.e. carrying individuals on the body while feeding.
Sharks possess brain-to-body mass ratios that are similar to mammals and birds, [89] and have exhibited apparent curiosity and behavior resembling play in the wild. [ 90 ] [ 91 ] There is evidence that juvenile lemon sharks can use observational learning in their investigation of novel objects in their environment.
Figure 1:In mammals, the quadrate and articular bones are small and part of the middle ear; the lower jaw consists only of dentary bone.. While living mammal species can be identified by the presence of milk-producing mammary glands in the females, other features are required when classifying fossils, because mammary glands and other soft-tissue features are not visible in fossils.