Avian clutch size of increasing clutch size with increasing latitude. The proximate and ultimate causes for this pattern have been a subject of intense debate involving the ideas of group and individual selection. David Lack observed a direct relationship between latitude and avian clutch size. Birds near the equator laid approximately half as many eggs as those that resided in northern temperate habitats. He observed an increasing clutch-size from the equator towards the poles (something he referred to as the “latitude trend”) for many passerine (perching) birds, near-passerine (tree-dwelling) birds and in various other groups: Strigiformes, Falconiformes, Ciconiiformes, Laridae, Ralliformes, Galliformes, Podicipedifomes, and
The Origin of Birds in fact, was decidedly reptilian and generally opposed to that of modern birds. This included the pelvis, which lacks a pectineal process and has a very different os sacrum from modern birds, as well as the carpus, which Heilmann wrote exhibited the same phenomena found in the wrists of modern reptiles. Its tail was also noted by Heilmann as being extremely reptilian and resembling nothing known of modern birds. He goes on to state that other features of "Archaeopteryx", however, are remarkably birdlike and bear little resemblance to their reptilian analogues. The hand of "Archaeopteryx" is observed as being one