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19-749: One of the first to study rocks of the Usili Formation was British geologist G. M. Stockley. In 1932, Stockley explored the geology of the Ruhuhu Basin in Tanzania. He called a series of layers dating from the Late Carboniferous to the Middle Triassic of the Songea Series and divided it into eight units labelled K1-K8. Stockley was also the first to describe fossils from these rocks, naming an older layer

38-474: A few hundred thousand years. The Pennsylvanian is named after the U.S. state of Pennsylvania , where the coal beds of this age are widespread. The division between Pennsylvanian and Mississippian comes from North American stratigraphy. In North America, where the early Carboniferous beds are primarily marine limestones , the Pennsylvanian was in the past treated as a full-fledged geologic period between

57-493: A trough cross-bedded, coarse-grained, sandstone-dominated interval that is 25 to 40 metres (82 to 131 ft) thick, overlain by massive nodular siltstone and laminated mudstone beds with minor ribbon sandstones forming the bulk of the succession. Since Parrington (1956), the Usili Formation became widely recognized as a Late Permian formation that correlates with the Teekloof and Balfour formations of South Africa , as well as with

76-592: The ICS geologic timescale , the younger of two subperiods of the Carboniferous Period (or the upper of two subsystems of the Carboniferous System). It lasted from roughly 323.2  million years ago  to 298.9  million years ago . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain by

95-534: The Idusi (K1), Mchuchuma (K2), Mbuyura (K3), Mhukuru (K4), Ruhuhu (K5), and Usili (K6) formations and the informal Manda Beds , which include the Kingori Sandstone (K7) and Lifua Member (K8). Recent studies have described the Usili Formation as a 260 metres (850 ft) thick fluvio - lacustrine succession made up of a lowermost conglomeratic interval that is approximately 5 meters thick, grading up into

114-798: The Zambian Upper Madumabisa Mudstone ( Cistecephalus AZ ). Comparison of Usili tetrapods with those of the lower Beaufort Group has suggested a broad biostratigraphic correlation with the Cistecephalus , Dicynodon , and Tropidostoma assemblage zones. Sidor et al. (2010) recognized only one undivided tetrapod faunal assemblage in the Usili Formation, which includes Aenigmastropheus , temnospondyls , pareiasaurs , gorgonopsians , therocephalians , cynodonts , and dicynodonts , whose remains were collected from various localities. This suggests that several therapsid genera have unequal stratigraphic ranges and temporal durations in

133-515: The end of the Permian , during which their cynodont descendants became smaller and nocturnal , as the reptilian archosaurs took over, although dicynodonts would remain megafaunal until their extinction at the end of the Triassic . Most pre-rainforest collapse tetrapods remained smaller, probably due to the land being primarily occupied by the gigantic millipedes, scorpions, and flying insects. After

152-729: The "Lower Bone Bed" and a younger layer the "Upper Bone Bed". In 1957, paleontologist Alan J. Charig described many more fossils from the upper bone beds in his Ph.D. thesis for the University of Cambridge . Subsequently, Stockley's units were renamed, Charig (1963) calling unit K6 the Kawinga Formation, K7 the Kingori Sandstones, and K8 the Manda Formation. Fossils were identified in many strata , invalidating Stockley's division into two distinct bone beds. Since Charig's description,

171-786: The Gzhelian plus the uppermost Kasimovian. The Missourian or Monongahela corresponds to the rest of the Kasimovian. The Desmoinesian or Allegheny corresponds to the upper half of the Moscovian. The Atokan or upper Pottsville corresponds to the lower half of the Moscovian. The Morrowan corresponds to the Bashkirian. In the European subdivision, the Carboniferous is divided into two epochs: Dinantian (early) and Silesian (late). The Silesian starts earlier than

190-645: The Kawinga Formation has been renamed the Usili Formation, the Kingori Sandstones have become the Kingori Sandstone Member of the Manda Formation , and Charig's original Manda Formation has become a subunit of the formation called the Lifua Member. Six formations and one informal unit are currently recognized in the Songea Group (Ruhuhu basin) rocks range in age from Pennsylvanian to Anisian , including

209-686: The Mississippian and the Permian . In parts of Europe, the Mississippian and Pennsylvanian are one more-or-less continuous sequence of lowland continental deposits and are grouped together as the Carboniferous Period. The current internationally used geologic timescale of the ICS gives the Mississippian and Pennsylvanian the rank of subperiods, subdivisions of the Carboniferous Period. All modern classes of fungi have been found in rocks of Pennsylvanian age. The major forms of life at this time were

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228-433: The Pennsylvanian and is divided in three ages: Aelurognathus Genus-level Species-level Aelurognathus is an extinct genus of gorgonopsian therapsids from the Permian of South Africa and Zambia . The type species is Aelurognathus tigriceps , originally named Scymnognathus tigriceps by South African paleontologists Robert Broom and Sydney H. Haughton in 1913, and later assigned to

247-1008: The Ruhuhu and Karoo basins. Sidor et al. (2010) and Sidor et al. (2013) noted that it is probable that the Chiweta Beds of Malawi and the Usili Formation of Tanzania represent the same rock unit, separated only by political boundaries and geologic faulting (being located on either side of Lake Nyasa ). Except for the burnetiid MAL 240, which is unique to the Chiweta Beds, the Usili Formation hosts identical genera, including Aelurognathus , Dicynodontoides , Rhachiocephalus , Endothiodon cf. E. bathystoma , Oudenodon baini , Gorgonops ? dixeyi and an indeterminate tusked dicynodont (SAM-PK-7862, SAM-PK-7863). Late Carboniferous The Pennsylvanian ( / ˌ p ɛ n s əl ˈ v eɪ n i . ən / pen-səl- VAYN -i-ən , also known as Upper Carboniferous or Late Carboniferous ) is, on

266-534: The arthropods. Arthropods were far larger than modern ones. Arthropleura , a giant millipede , was a common sight and the giant griffinfly Meganeura "flew the skies". It is commonly considered that is because of high oxygen level, however some of those large arthropod records are also known from period with relatively low oxygen, which suggest high oxygen pressure may not have been a primary reason for their gigantism. Amphibians were diverse and common; some were several meters long as adults. The collapse of

285-563: The back of the skeleton are the most scattered, suggesting that the Aelurognathus individuals fed on the rear of the carcass, removing the hind limbs to reach the soft underside. The small incisor teeth of Aelurognathus indicate that it was not able to crush bone but more likely stripped flesh from its prey like the modern-day wild dog Lycaon pictus . Bite marks on the bones of the skeleton were unlikely to have been made by Aelurognathus and may be an indication that another predator killed

304-428: The earliest sauropsid reptiles ( Hylonomus ), and the earliest known " pelycosaur " synapsids ( Archaeothyris ). Small lizard-like animals quickly gave rise to many descendants. Amniotes underwent a major evolutionary radiation, in response to the drier climate that followed the rainforest collapse . For some reason, pelycosaurs were able to reach larger sizes before reptiles could, and this trend continued until

323-512: The new genus Aelurognathus by Haughton in 1924. Scymnognathus parringtoni von Huene, 1950, previously assigned to Aelurognathus , is now classified as a species of Sauroctonus . Aelurognathus nyasaensis Haughton, 1926 is not referable to the genus. A broken tooth beside the skeleton of a dicynodont from the Tropidostoma Assemblage Zone has been attributed to Aelurognathus , indicating that it scavenged. The bones of

342-487: The rainforest collapse, the giant arthropods disappeared, allowing amniote tetrapods to achieve larger sizes. The Pennsylvanian has been variously subdivided. The international timescale of the ICS follows the Russian subdivision into four stages: North American subdivision is into five stages, but not precisely the same, with additional (older) Appalachian series names following: The Virgilian or Conemaugh corresponds to

361-483: The rainforest ecology in the mid-Pennsylvanian (between the Moscovian and the Kasimovian) removed many amphibian species that did not survive as well in the cooler, drier conditions. Amniotes, however, prospered due to specific key adaptations. One of the greatest evolutionary innovations of the Carboniferous was the amniote egg, which allowed for the further exploitation of the land by certain tetrapods . These included

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