a few lineages, although the precise mechanism of the extinction is unclear. Before the event, oceans and lakes were dominated by lobe-finned fishes and armored fishes called placoderms. After the gap, modern ray finned fish, as well as sharks and their relatives were the dominant forms. The period also saw the demise of the Ichthyostegalia, the early fish-like amphibians with more than five digits. The low diversity of marine fishes, particularly shell-crushing predators (durophages), at the beginning of Romer's gap is supported by the sudden abundance of hard-shelled crinoid echinoderms during the same period. The Tournaisian has even been called the "Age of Crinoids". Once the number of shell-crushing ray-finned fishes and sharks increased later in the Carboniferous, coincident with the end of Romer's gap, the diversity of crinoids with Devonian-type armor plummeted, following the pattern of a classic predator-prey (Lotka-Volterra) cycle. There is increasing evidence that lungfish and stem tetrapods and amphibians recovered quickly and diversified in the rapidly changing environment of the end-Devonian and Romer's Gap. Gap fauna The gap in the tetrapod record has been progressively closed with the discoveries of such early Carboniferous tetrapods as Pederpes and Crassigyrinus. There are a few sites where vertebrate fossils have been found to help fill in the gap, such as the East Kirkton Quarry, in Bathgate, Scotland, a long-known fossil site that was revisited by Stanley P. Wood in 1984 and has since been revealing a number of early tetrapods in the mid Carboniferous; "literally dozens of tetrapods came rolling out: Balanerpeton (a temnospondyl), Silvanerpeton and Eldeceeon (basal anthracosaurs), all in multiple copies, and one spectacular proto-amniote, Westlothiana", Paleos Project reports. In 2016, five new species were found across the Ballagan Formation: Perittodus apsconditus, Koilops herma, Ossirarus kierani, Diploradus austiumensis, Aytonerpeton microps. These stem tetrapods and amphibians provide evidence for an early split between the two groups, and rapid diversification in the Early Carboniferous. However, tetrapod material in the earliest stage of the Carboniferous, the Tournaisian, remains scarce relative to fishes in the same habitats, which can appear in large death assemblages, and is unknown until late in the stage. Fish faunas from Tournaisian sites around the world are very alike in composition, containing common and ecologically similar species of ray-finned fishes, rhizodont lobe-finned fishes, acanthodians, sharks, and holocephalans. Recent analysis of the Blue Beach deposits in Nova Scotia suggest that "the early tetrapod fauna is not easily divisible