Isalo II Formation
Stratigraphic range: Ladinian-Carnian
TypeGeological formation
Unit ofIsalo Group
UnderliesIsalo III Formation (unconformity)
OverliesIsalo I Formation
Lithology
PrimarySandstone, mudstone
Location
Coordinates20°18′S 45°24′E / 20.3°S 45.4°E / -20.3; 45.4
Approximate paleocoordinates23°06′S 24°42′E / 23.1°S 24.7°E / -23.1; 24.7
RegionMahajanga & Toliara Provinces
Country Madagascar
ExtentMorondava Basin, Mahajanga Basin
Isalo II is located in Madagascar
Isalo II
Isalo II (Madagascar)

Isalo II, also known as the Makay Formation, is an informal Triassic geological unit in Madagascar.[1]

It is described as "thick beds of mottled red or green clays associated with soft cross-bedded sandstones, light in colour and much finer-grained than the Isalo I sandstones." It is prominent in the Makay Massif.[2]

Fossil content

Amphibians

Amphibians
Taxon Material Notes
Metoposauridae indet. An interclavicle, skull fragments, and intercentra Indeterminate metoposaurid remains similar to those of Indian metoposaurids. Some fossils were the basis for the dubious species "Metoposaurus hoffmani". May be from Isalo II or III.[3]
Stereospondyli indet. Interclavicles Indeterminate stereospondyl remains. May be from Isalo II or III.[3]

Reptiles

Synapsids
Taxon Material Notes
Archosauriformes sp. Teeth, a coracoid, a centrum fragment, and cranial fragments Various indeterminate fragments, some of which may belong to dinosaurs.[4]
Azendohsaurus madagaskarensis[5] Numerous skulls and postcranial fossils[1] An allokotosaurian archosauromorph,[6][7][1] originally mistakenly identified as a "prosauropod" dinosaur.[5]
Isalorhynchus genovefae Numerous fossils representing parts of the skull and postcrania A rhynchosaur sometimes considered a species of Hyperodapedon.[8] Possibly represents two taxa.[9] Reported sphenodontian[5] fossils are most likely juvenile rhynchosaurs instead.[10]
Kongonaphon kely[11] A maxilla and postcranial material A tiny lagerpetid avemetatarsalian[12]
Mambachiton fiandohana[13] A partial skeleton An armored basal avemetatarsalian[14]
Phytosauria indet. Teeth Similar to Rutiodon teeth.[4]
Procolophonidae sp. A jaw fragment and other remains An unnamed procolophonid parareptile[8]
Pseudosuchia indet. Osteoderms Likely referable to stagonolepid aetosaurs, though similar to goniopholidid crocodylomorphs as well.[4]
Silesauridae sp. An unnamed silesaurid dinosauromorph[14]

Synapsids

Synapsids
Taxon Material Notes
Chiniquodon kalanoro[15] Part of a jaw A chiniquodontid cynodont
Dadadon isaloi[16] Several skulls and jaw fragments[17][18] A massetognathine[18] traversodontid cynodont
Kannemeyeriiformes sp. An unnamed kannemeyeriiform dicynodont[5][15][1]
Menadon besairiei[16] Skulls, jaws, and postcranial material[19] A traversodontid cynodont

References

  1. 1 2 3 4 Nesbitt, S.J.; Flynn, J.J.; Pritchard, A.C.; Parrish, M.J.; Ranivoharimanana, L.; Wyss, A.R. (2015). "Postcranial osteology of Azendohsaurus madagaskarensis (?Middle to Upper Triassic, Isalo Group, Madagascar) and its systematic position among stem archosaur reptiles". Bulletin of the American Museum of Natural History. 398: 1–126. doi:10.1206/amnb-899-00-1-126.1. hdl:2246/6624. ISSN 0003-0090. S2CID 86289421.
  2. ↑ Brenon, P. (1972). The Geology of Madagascar. In: Battistini, R., Richard-Vindard, G. (eds) Biogeography and Ecology in Madagascar. Monographiae Biologicae, vol 21. Springer, Dordrecht. https://doi.org/10.1007/978-94-015-7159-3_2
  3. 1 2 Fortuny, Josep; Arbez, Thomas; Mujal, Eudald; Steyer, J. Sébastien (2019-01-02). "Reappraisal of 'Metoposaurus hoffmani' Dutuit, 1978, and description of new temnospondyl specimens from the Middle–Late Triassic of Madagascar (Morondava Basin)". Journal of Vertebrate Paleontology. 39 (1): e1576701. Bibcode:2019JVPal..39E6701F. doi:10.1080/02724634.2019.1576701. ISSN 0272-4634. S2CID 146075668.
  4. 1 2 3 Burmeister, Kurtis C.; Flynn, John J.; Parrish, J. Michael; Wyss, Andre R. (2006). "Paleogeographic and biostratigraphic implications of new early Mesozoic vertebrates from Poamay, central Morondava Basin, Madagascar". New Mexico Museum of Natural History & Science Bulletin. 37: 457–475.
  5. 1 2 3 4 Flynn, John J.; Parrish, J. Michael; Rakotosamimanana, Berthe; Simpson, William F.; Whatley, Robin L.; Wyss, André R. (1999-10-22). "A Triassic Fauna from Madagascar, Including Early Dinosaurs". Science. 286 (5440): 763–765. doi:10.1126/science.286.5440.763. ISSN 0036-8075. JSTOR 2899382. PMID 10531059.
  6. ↑ Flynn, John; Nesbitt, Sterling; Parrish, Michael; Ranivoharimanana, Lovasoa; Wyss, Andre (2008). "A new species of basal archosauromorph from the Late Triassic of Madagascar". Journal of Vertebrate Paleontology. 28 (sup3): 78A.
  7. ↑ Flynn, John J.; Nesbitt, Sterling J.; Parrish, J. Michael; Ranivoharimanana, Lovasoa; Wyss, André R. (2010). "A new species of Azendohsaurus (Diapsida: Archosauromorpha) from the Triassic Isalo Group of southwestern Madagascar: cranium and mandible". Palaeontology. 53 (3): 669–688. Bibcode:2010Palgy..53..669F. doi:10.1111/j.1475-4983.2010.00954.x. ISSN 1475-4983. S2CID 82341339.
  8. 1 2 Langer, Max; Boniface, Michael; Cuny, Gilles; Barbieri, Laurent (2000-04-01). "The phylogenetic position of Isalorhynchus genovefae, a Late Triassic rhynchosaur from Madagascar" (PDF). Annales de Paléontologie. 86 (2): 101–127. Bibcode:2000AnPal..86..101L. doi:10.1016/S0753-3969(00)80002-6. ISSN 0753-3969.
  9. ↑ Whatley, R.L.; Flynn, J.J.; Parrish, J.M.; Simpson, W.; Wyss, A.R. (1999). "Isalorhynchus revisited: two rhynchosaur skeletons from southwestern Madagascar". Journal of Vertebrate Paleontology. 19 (sup3): 84A. JSTOR 4524027.
  10. ↑ Langer, Max Cardoso (2005). "Studies on continental Late Triassic tetrapod biochronology. II. The Ischigualastian and a Carnian global correlation" (PDF). Journal of South American Earth Sciences. 19 (2): 219–239. doi:10.1016/j.jsames.2005.04.002. ISSN 0895-9811.
  11. ↑ Kammerer, Christian F.; Nesbitt, Sterling J.; Flynn, John J.; Ranivoharimanana, Lovasoa; Wyss, André R. (2020-07-02). "A tiny ornithodiran archosaur from the Triassic of Madagascar and the role of miniaturization in dinosaur and pterosaur ancestry". Proceedings of the National Academy of Sciences. 117 (30): 17932–17936. Bibcode:2020PNAS..11717932K. doi:10.1073/pnas.1916631117. ISSN 0027-8424. PMC 7395432. PMID 32631980. S2CID 220386589.
  12. ↑ Kammerer, Christian F.; Nesbitt, Sterling J.; Flynn, John J.; Ranivoharimanana, Lovasoa; Wyss, Andre (October 2019). "A new lagerpetid archosaur from the Triassic of Madagascar and the importance of miniaturization in ornithodiran evolution". Society of Vertebrate Paleontology Abstracts of Papers, 79th Annual Meeting: 127. Archived from the original on 2020-12-15. Retrieved 2020-06-27.
  13. ↑ Nesbitt, Sterling J.; Patellos, Emily; Kammerer, Christian F.; Ranivoharimanana, Lovasoa; Wyss, Andre´ R.; Flynn, John J. (25 July 2023). "The earliest-diverging avemetatarsalian: a new osteoderm-bearing taxon from the Triassic (?Earliest Late Triassic) of Madagascar and the composition of avemetatarsalian assemblages prior to the radiation of dinosaurs". Zoological Journal of the Linnean Society. 199 (zlad038): 327–353. doi:10.1093/zoolinnean/zlad038.
  14. 1 2 Patellos, Emily A.; Nesbitt, Sterling J.; Kammerer, Christian F.; Wyss, Andre; Flynn, John J.; Ranivoharimanana, Lovasoa (October 2019). "A new reptile from the ?Middle Triassic of Madagascar may represent the earliest-diverging Avemetatarsalia (Archosauria)". Society of Vertebrate Paleontology Abstracts of Papers, 79th Annual Meeting: 167. Archived from the original on 2020-12-15. Retrieved 2020-06-27.
  15. 1 2 Kammerer, Christian F.; Flynn, John J.; Ranivoharimanana, Lovasoa; Wyss, André R. (2010-12-02). "The first record of a probainognathian (Cynodontia: Chiniquodontidae) from the Triassic of Madagascar". Journal of Vertebrate Paleontology. 30 (6): 1889–1894. Bibcode:2010JVPal..30.1889K. doi:10.1080/02724634.2010.520784. ISSN 0272-4634. JSTOR 25790814. S2CID 85868922.
  16. 1 2 Flynn, John J.; Parrish, J. Michael; Rakotosamimanana, Berthe; Ranivoharimanana, Lovasoa; Simpson, William F.; Wyss, André R. (2000-09-25). "New Traversodontids (Synapsida: Eucynodontia) from the Triassic of Madagascar". Journal of Vertebrate Paleontology. 20 (3): 422–427. doi:10.1671/0272-4634(2000)020[0422:NTSEFT]2.0.CO;2. ISSN 0272-4634. S2CID 130041740.
  17. ↑ Ranivoharimanana, Lovasoa; Kammerer, Christian F.; Flynn, John J.; Wyss, André R. (2011-11-01). "New material of Dadadon isaloi (Cynodontia, Traversodontidae) from the Triassic of Madagascar". Journal of Vertebrate Paleontology. 31 (6): 1292–1302. Bibcode:2011JVPal..31.1292R. doi:10.1080/02724634.2011.618154. ISSN 0272-4634. JSTOR 41407685. S2CID 220437281.
  18. 1 2 Kammerer, Christian F.; Flynn, John J.; Ranivoharimanana, Lovasoa; Wyss, André R. (October 2012). "Ontogeny in the Malagasy Traversodontid Dadadon isaloi and a Reconsideration of its Phylogenetic Relationships". Fieldiana Life and Earth Sciences. 2012 (5): 112–125. doi:10.3158/2158-5520-5.1.112. ISSN 2158-5520. S2CID 84651546.
  19. ↑ Kammerer, Christian F.; Flynn, John J.; Ranivoharimanana, Lovasoa; Wyss, André R. (2008-06-12). "New material of Menadon besairiei (Cynodontia: Traversodontidae) from the Triassic of Madagascar". Journal of Vertebrate Paleontology. 28 (2): 445–462. doi:10.1671/0272-4634(2008)28[445:NMOMBC]2.0.CO;2. ISSN 0272-4634. S2CID 140720709.
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