Usili Formation | |
---|---|
Stratigraphic range: Lopingian ~ | |
Type | Geological formation |
Unit of | Songea Group |
Underlies | Manda Formation |
Overlies | Ruhuhu Formation |
Thickness | 260 m (850 ft) |
Lithology | |
Primary | Sandstone, conglomerate |
Other | Siltstone, mudstone |
Location | |
Coordinates | 10°18′S35°06′E / 10.3°S 35.1°E |
Approximate paleocoordinates | 55°06′S15°12′E / 55.1°S 15.2°E |
Region | Ruvuma Region |
Country | Tanzania |
Extent | Ruhuhu Basin |
Type section | |
Named for | Usili Mountain |
Named by | Stockley |
Year defined | 1932 |
The Usili Formation is a Late Permian geologic formation in Tanzania. It preserves fossils of many terrestrial vertebrates from the Permian, including temnospondyls, pareiasaurs, therapsids and the archosauromorph Aenigmastropheus . [1] [2]
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 the "Lower Bone Bed" and a younger layer the "Upper Bone Bed". [3]
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. [4] [5] 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, 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. [3] Six formations and one informal unit are currently recognized in the Songea Group (Ruhuhu basin) rocks range in age from Pennsylvanian to Anisian, including 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). [6]
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 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 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 the Ruhuhu and Karoo basins. [2] [6]
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). [1] [6]
Color key
| Notes Uncertain or tentative taxa are in small text; |
Taxon | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
Peltobatrachus | P. pustulatus | A stereospondyl, endemic to this formation. | |||
Taxon | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
Anthodon | A. serrarius | A pareiasaur. Originally named Anthodon minisculus, it was considered a junior synonym of A. serrarius by Lee (1997). | |||
Pareiasaurus | P. serridens | A pareiasaur. | |||
Unidentified Parareptilia | Indeterminate | GPIT K72, six or seven dorsal vertebrae with articulated osteoderms | A pareiasaur originally described by von Huene (1944), endemic to this formation. | ||
Taxon | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
Aenigmastropheus | A. parringtoni | B35 | UMZC T836, a partial postcranial skeleton including five posterior cervical and anterior dorsal vertebrae, the distal half of the right humerus, a fragment of probable left humeral shaft, the proximal end of the right ulna, and three indeterminate fragments of bone, one of which may represent a partial radius. | A protorosaurid archosauromorph, endemic to this formation. | |
Taxon | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
Compsodon | C. helmoedi [7] | L35, Z04 | A highly damaged mandible as well as articulated craniodental remains (skull and mandible) | First preservation of a mandible for this taxon. | |
Daptocephalus | D .leoniceps | A dicynodontoid dicynodont, previously considered to be a species of Dicynodon , known only from South Africa. | |||
D. huenei | B2 (Kingori) | SAM-PK-10630, fragmentary skull and postcrania; 7 additional skulls | A dicynodontoid dicynodont, the holotype was formerly assigned as a species of Dicynodon. | ||
Dicynodon | Dicynodon lacerticeps | A dicynodontoid dicynodont, known only from South Africa. | |||
Dicynodon angielczyki | UMZC T1089, a complete skull; 6 additional partial to complete skulls and some possible postcrania | A species named for specimens of Dicynodon formerly assigned to Daptocephalus huenei. [8] | |||
Dicynodon | D. robertsi | Originally considered to be a species of Dicynodon, but it is a junior synonym of Oudenodon bainii . | |||
"Dicynodon" tealei | B32 | SAM-PK-10631, fragmentary skull roof | An indeterminate dicynodont, a nomen dubium . | ||
Dicynodontoides | D. nowacki | Kingori | GPIT/RE/7174, a nearly complete skull; other skulls and skeletons | A kingoriid dicynodont, previously considered to be a species of Dicynodon. | |
Endothiodon | E. cf. bathystoma | Basal dicynodont, endothiodontid. | |||
E. sp. nov. | A new, yet unnamed species. | ||||
E. uniseries | Basal dicynodont, endothiodontid. Originally placed in its own genus Esoterodon. | ||||
Euptychognathus | E. bathyrhynchus | Kingori | GPIT/RE/7104 (UT K 19), well preserved partial skull | Basal lystrosaurid dicynodont, previously considered to be a species of Dicynodon. | |
Geikia | G. locusticeps | GPIT K87/UT von HUENE 1942 Abb.3, juvenile partial skull and dentary; GPIT K114, skull and dentary | A geikiine cryptodont, previously considered to be a species of Dicynodon. | ||
Katumbia | K. parringtoni | B19 (Kingori); B4 (Katumbi); Usili-Berges | GPIT K120/UT Huene 1942 S.155, fragmentary skull; UMZC T761, UMZC T791, incomplete skulls; A dentary | Basal dicynodontoid, endemic to this formation. | |
Kawingasaurus | K. fossilis | Kingori | UT K 52, skull and dentary; UT K 56, skull; UT K 55, 5 skulls and postcrania | A cistecephalid dicynodont, endemic to this formation. | |
Oudenodon | O. bainii | Many skulls | Basal oudenodontid cryptodont. | ||
Pachytegos | P. stockleyi | B32 | SAM 10639, SAM 10642, fragmentary skull elements | Basal dicynodont, endothiodontid, endemic to this formation. | |
Pristerodon | P. mackayi | NMT RB38 | Basal dicynodont, eumantellid. Previous reports by King (1988, 1992), King and Rubidge (1993), and Gay and Cruickshank (1999) were based on the holotype specimen of Katumbia parringtoni. The first diagnostic specimen of Pristerodon mackayi from this formation, NMT RB38, was discovered in 2008. | ||
Rhachiocephalus | R. behemoth | GPIT K 15, nearly complete skull; GPIT K 15B, fragmentary skull | A rhachiocephalid cryptodont. | ||
R. magnus | Many specimens | A rhachiocephalid cryptodont. | |||
Unnamed Anomodont | Unidentified | NMT RB22, a partial maxilla of an adult. NMT RB156, a nearly complete skull, mandible, and associated postcrania of a subadult. | A new genus and species of a cryptodontian dicynodont. Endemic to this formation. | ||
Taxon | Locality | Material | Notes | Images |
---|---|---|---|---|
Burnetiidae indet. | NMT RB4, partial isolated skull roof; NMT RB36, fragmentary right dorsal margin of the orbit | A burnetiid most closely related to Burnetia mirabilis from the Dicynodon AZ of South Africa. Too fragmentary to be assigned to a new taxon, its morphology is unique among Cistecephalus AZ taxa. | ||
Taxon | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
Procynosuchus | P. delaharpeae | IGP K 92, fragmentary skull | A procynosuchid | ||
Taxon | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
Silphictidoides | S. ruhuhuensis | Kingori | K 70, nearly complete skull and dentary; K 125, nearly complete skull, dentary and right humerus | A baurioid, endemic to this formation. | |
Theriognathus | T. microps | Kingori | K 107 and K 84, two fragmentary skulls | A whaitsiid | |
Taxon | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
Cyonosaurus | C. broomianus | A gorgonopsian | |||
Dinogorgon | D. rubidgei | Kingori | IGP K 16, nearly complete skull and dentary | A gorgonopsid, endemic to this formation. | |
"Dixeya" | "Dixeya" nasuta | IGP K 52, nearly complete skull; IGP K 96, fragmentary skull; 6 more skulls | A gorgonopsid, informally given the nomen nudum "Njalila" by Gebauer (2007). Endemic to this formation. | ||
Gorgonops | G. sp. | A gorgonopsid | |||
Inostrancevia | I. sp. | NMT RB38, an isolated left premaxilla [9] | A gorgonopsid | ||
Lycaenops | L. sp. | A gorgonopsid | |||
Rubidgea | R. atrox | IGP K 46, fragmentary skull | A gorgonopsid, formally named Broomicephalus, endemic to this formation. | ||
Ruhuhucerberus | R. haughtoni | Katumbi, B4 | MZC T891, nearly complete skull | A gorgonopsid, endemic to this formation. | |
Sauroctonus | S. parringtoni | Usili-Berges | IGP U 28, complete skull and dentary and fragmentary skeleton | A gorgonopsid, endemic to this formation. | |
Scylacops | S. capensis | Kingori, B19 | MZC T885/FRP 93, skull and cervical vertebrae | A gorgonopsid | |
Sycosaurus | S. nowaki | Kingori | IGP K 47, nearly complete skull | A gorgonopsid, endemic to this formation. | |
Nyasasaurus is an extinct genus of avemetatarsalian archosaur from the putatively Middle Triassic Manda Formation of Tanzania that may be the earliest known dinosaur. The type species Nyasasaurus parringtoni was first described in 1956 in the doctoral thesis of English paleontologist Alan J. Charig, but it was not formally described until 2013.
The Daptocephalus Assemblage Zone is a tetrapod assemblage zone or biozone found in the Adelaide Subgroup of the Beaufort Group, a majorly fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa. This biozone has outcrops located in the upper Teekloof Formation west of 24°E, the majority of the Balfour Formation east of 24°E, and the Normandien Formation in the north. It has numerous localities which are spread out from Colesberg in the Northern Cape, Graaff-Reniet to Mthatha in the Eastern Cape, and from Bloemfontein to Harrismith in the Free State. The Daptocephalus Assemblage Zone is one of eight biozones found in the Beaufort Group and is considered Late Permian (Lopingian) in age. Its contact with the overlying Lystrosaurus Assemblage Zone marks the Permian-Triassic boundary.
The Cynognathus Assemblage Zone is a tetrapod biozone utilized in the Karoo Basin of South Africa. It is equivalent to the Burgersdorp Formation, the youngest lithostratigraphic formation in the Beaufort Group, which is part of the fossiliferous and geologically important Karoo Supergroup. The Cynognathus Assemblage Zone is the youngest of the eight biozones found in the Beaufort Group, and is considered to be late Early Triassic (Olenekian) to early Middle Triassic (Anisian) in age. The name of the biozone refers to Cynognathus crateronotus, a large and carnivorous cynodont therapsid which occurs throughout the entire biozone.
Endothiodon is an extinct genus of medium to large dicynodont from the Late Permian. Like other dicynodonts, Endothiodon was an herbivore, but it typically lacked the two tusks that characterized most other dicynodonts and instead had long rows of teeth inset in the jaws that replaced in waves. The anterior portion of the upper and lower jaw are curved upward, creating a distinct beak that is thought to have allowed them to be specialized grazers.
Dicynodontoides is a genus of small to medium-bodied, herbivorous, emydopoid dicynodonts from the Late Permian. The name Dicynodontoides references its “dicynodont-like” appearance due to the caniniform tusks featured by most members of this infraorder. Kingoria, a junior synonym, has been used more widely in the literature than the more obscure Dicynodontoides, which is similar-sounding to another distantly related genus of dicynodont, Dicynodon. Two species are recognized: D. recurvidens from South Africa, and D. nowacki from Tanzania.
Daptocephalus is an extinct genus of dicynodont synapsid, which was found in Late Permian strata, in a biozone known precisely for the presence of fossils of this dicynodont, the Daptocephalus Assemblage Zone, in the Karoo Basin in South Africa. An additional species, D. huenei, is known from the Usili Formation in Tanzania and was formerly assigned to the genus Dicynodon before a study in 2019 recognised that the type specimen belonged to Daptocephalus.
Geikia is an extinct genus of dicynodont therapsids from the late Permian. The abundance and diversity of dicynodonts during this period, combined with incomplete or inadequately prepared specimens, have led to challenges in determining relationships within this taxon. Only two species, Geikia locusticeps and Geikia elginensis have been assigned to this genus. While this is the currently accepted classification, fossil record limitations have led to repeated debate on the genus assignments of these species.
Kawingasaurus is an extinct genus of dicynodont therapsid from the Late Permian Usili Formation of Tanzania. It is a member of the family Cistecephalidae, and like other cistecephalids it is thought to have been fossorial. It is a member of the family Cistecephalidae. Cistephalidae includes genera Cisteceohalus, Cistecephaloides and Kawingasaurus. Greek for Saurus meaning “lizard” appears as a suffix denoting a reptilian origin. Living between 254.17 and 259.9 million years ago in the late Permian and believed to have the first and last recorded appearance in this time period. It lived in deep burrows as a suggested by most burrowing dicynodonts from evaluation of cranial sutures, vestibule inflation and enlarged stapes foot plates which are thought to be functionally correlated with bone-conduction hearing; all observed in fossorial vertebrates which use seismic signals as communication.
Sangusaurus is an extinct genus of large dicynodont synapsid with two recognized species: S. edentatus and S. parringtonii. Sangusaurus is named after the Sangu stream in eastern Zambia near to where it was first discovered + ‘saur’ which is the Greek root for lizard. Sangusaurus fossils have been recovered from the upper parts of the Ntawere Formation in Zambia and of the Lifua Member of the Manda Beds in Tanzania. The earliest study considered Sangusaurus a kannemeyeriid dicynodont, but more recent phylogenetic analyses place Sangusaurus within the stahleckeriid clade of Dicynodontia. Until recently, little work had been done to describe Sangusaurus, likely due to the fact that only four incomplete fossil specimens have been discovered.
Rechnisaurus is an extinct genus of dicynodont from the Middle Triassic (Anisian) Yerrapalli Formation of India. It contains a single species, Rechnisaurus cristarhynchus.
Tetragonias is an extinct genus of dicynodont from the Anisian Manda Beds of Tanzania. With tetra meaning “four,” and goni meaning “angle,” the name references the square shape of the Tetragonias skull when viewed dorsally. Not to be confused with the plant Tetragonia,Tetragonias were dicynodont anomodonts discovered in the late 1960s by paleontologist A. R. I. Cruickshank in the Manda Formation. Only the type species, T. njalilus, has been recognized.
Katumbia is a genus of dicynodont from Late Permian (Changhsingian) Kawinga Formation of the Ruhuhu Basin, Tanzania. and possibly the Upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia. The type species, K. parringtoni, was originally referred to the genus Cryptocynodon, which is now recognized as a junior synonym of Endothiodon.
Christian Alfred Sidor is an American vertebrate paleontologist. He is currently a Professor in the Department of Biology, University of Washington in Seattle, as well as Curator of Vertebrate Paleontology and Associate Director for Research and Collections at the Burke Museum of Natural History and Culture. His research focuses on Permian and Triassic tetrapod evolution, especially on therapsids.
Stenaulorhynchus is an extinct genus of hyperodapedontid rhynchosaur known from the Middle Triassic deposits of Tanganyika Territory, Tanzania. It was found in the Lifua Member of the Manda Formation in the Karoo Supergroup. It was named and first described by Sidney Henry Haughton in 1932. The type species is Stenaulorhynchus stockleyi, a beaked herbivore measuring 1–6 meters in length.
Syops is an extinct genus of dicynodont therapsid. The type species S. vanhoepeni was first named in 1938 as Dicynodon vanhoepeni. Fossils of the genus have been found in the Cistecephalus Assemblage Zone in the Usili Formation of the Ruhuhu Basin, Tanzania and the Upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia. Its phylogenetic placement is somewhat uncertain, with multiple different studies finding it as either a basal geikiid, rhachiocephalid a dicynodontoid more derived than the most basal genera but less derived than Lystrosauridae, or a lystrosaurid.
The Manda Formation is a Middle Triassic (Anisian?) or possibly Late Triassic (Carnian?) geologic formation in Tanzania. It preserves fossils of many terrestrial vertebrates from the Triassic, including some of the earliest dinosauromorph archosaurs. The formation is often considered to be Anisian in age according to general tetrapod biochronology hypotheses and correlations to the Cynognathus Assemblage Zone of South Africa. However, some recent studies cast doubt to this age, suggesting that parts deposits may actually be younger (Carnian) in age.
Francis Rex Parrington was a British vertebrate palaeontologist and comparative anatomist at the University of Cambridge. A Fellow of the Royal Society, he was director of the Cambridge University Museum of Zoology and past president of the zoology section of the British Association for the Advancement of Science.
Asperoris is an extinct genus of archosauriform reptile known from the Middle Triassic Manda Beds of southwestern Tanzania. It is the first archosauriform known from the Manda Beds that is not an archosaur. However, its relationships with other non-archosaurian archosauriforms are uncertain. It was first named by Sterling J. Nesbitt, Richard J. Butler and David J. Gower in 2013 and the type species is Asperoris mnyama. Asperoris means "rough face" in Latin, referring to the distinctive rough texture of its skull bones.
Aenigmastropheus is an extinct genus of early archosauromorph reptiles known from the middle Late Permian Usili Formation of Songea District, southern Tanzania. It contains a single species, Aenigmastropheus parringtoni, known solely from UMZC T836, a partial postcranial skeleton of a mature individual. It was collected in 1933, and first described in 1956, as a "problematic reptile" due to its unique morphology. Therefore, a binomial name was erected for this specimen in 2014. Aenigmastropheus was probably fully terrestrial.
The Ntawere Formation is a Middle Triassic (Anisian) geological formation in Zambia, preserving fossils of synapsids, archosaurs, and temnospondyls.