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  • 21 Aug, 2019

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Maevarano Formation
The Maevarano Formation is a Late Cretaceous sedimentary rock formation found in the Mahajanga Province of northwestern Madagascar. It is most likely Maastrichtian in age, and records a seasonal, semiarid environment with rivers that had greatly varying discharges. Notable animal fossils recovered include the theropod dinosaur Majungasaurus, the early bird Vorona, the paravian Rahonavis, the titanosaurian sauropod Rapetosaurus, and the giant frog Beelzebufo.

Description

The Maevarano Formation is well exposed in the Mahajanga Basin, in particular near the village of Berivotra near the northwestern coast of the island where its outcrops have been heavily dissected by erosion. At the time it was being deposited, its latitude was between 30°S and 25°S as Madagascar drifted northward after splitting from India about 88 million years ago. It is composed of three smaller units or members. The lowest is the Masorobe Member, which is usually reddish and is at least 80 metres (260 ft). Its rocks are mostly poorly sorted coarse-grained sandstones with some finer-grained beds. It is separated by an erosional disconformity from the next member, the Anembalemba Member. The lower portion of the Anembalemba Member is fine to coarse clay-rich sandstone, whitish or light grey in color, with cross-bedding. The upper portion of this member is made of poorly sorted clay-rich sandstone, light olive-grey in color, that lacks cross-bedding. Most vertebrate fossils come from the Anembalemba Member, especially from the upper portion. The Miadana Member, the third and uppermost member, is not always present, and is up to 25 metres (82 ft) in some places. Elsewhere, it is replaced by the marine Berivotra Formation. The Miadana Member is made up of claystone, siltstone, and sandstone, lacks cross-bedding, and has several colors of rock. The Maevarano Formation as a whole is underlain by the Marovoay beds and capped by the Berivotra Formation.

The age of the Maevarano Formation has been debated; the Berivotra Formation, which is partially contemporaneous with the upper portions of the formation, shows that at least the upper part of the Maevarano is Maastrichtian in age. There is no evidence that it is Campanian, despite previous reports to that effect. The Berivotra Formation appears to include near its top a magnetic reversal, interpreted as the shift from Chron 30N to Chron 29R, which occurred approximately 65.8 million years ago (about 300,000 years before the Cretaceous–Paleogene boundary and associated Cretaceous–Paleogene extinction event. This suggests that Maevarano organisms also lived shortly before (geologically speaking) the extinction event.

History of exploration

The Maevarano Formation was first explored by French military physician Dr. Félix Salètes and his staff officer Landillon in 1895, and fossils and geologic data were sent to paleontologist Charles Depéret. He briefly described the formation and named two dinosaurs from the remains (Titanosaurus madagascariensis and Megalosaurus crenatissimus, now Majungasaurus). Similar collections were made throughout the 20th century, yielding mostly fragmentary fossils; one such specimen, a rough partial skull roof, became the holotype of supposed pachycephalosaur (bonehead dinosaur) Majungatholus in 1979. (This specimen was later shown to be part of the skull ornamentation of a Majungasaurus.) Large-scale expeditions (seven to date), under the banner of the Mahajanga Basin Project, began in 1993. These expeditions, conducted jointly by Stony Brook University and the University of Antananarivo, have greatly expanded knowledge of this formation and the organisms that lived while it was being deposited.

Paleoenvironment

The interpretation of Majungasaurus, Masiakasaurus, and Rapetosaurus during the late Cretaceous

The Maevarano Formation is interpreted as a low-relief alluvial plain that over time was covered by a marine transgression. Broad, shallow rivers flowed to the northwest from central highlands; evidence for debris flows suggests that the discharges of the rivers varied greatly, with periods of dilute water flow, and periods of rapid erosion dumping sediment into the channels. Paleosols are reddish and include root casts. The paleosols and other sedimentologic evidence indicate well-drained floodplains with abundant vegetation adapted to a relatively dry climate, strongly seasonal (rainy and dry seasons) and at times semiarid (not unlike the present climate of the area).

Paleofauna

Animals found in the formation include frogs (including Beelzebufo ampinga), turtles, snakes, lizards, at least seven species of crocodyliforms (including species of Mahajangasuchus and Trematochampsa), abelisaurid theropods Majungasaurus, noasaurid Masiakasaurus, two types of titanosaurian sauropods (Rapetosaurus and Vahiny), and at least five species of bird-like dinosaurs, including Rahonavis. The 6 to 7 metres (20 to 23 ft) long Majungasaurus was likely the apex predator in the terrestrial environment. Crocodyliforms were very diverse and abundant.

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Invertebrates

Invertebrates
Genus Species Location Stratigraphic position Material Notes Images
Cubiculum C. ornatus Ovoid chambers in dinosaur bones A trace fossil, possibly puppal chambers of carrion beetles
Ethmosestheria E. mahajangaensis Anembalemba Member A species of antronstheriid clam shrimp
Osteocallis O. mandibulus Curved grooves on dinosaur bones A trace fossil, possibly feeding marks by a similar insect as Cubiculum ornatus

Fish

Osteichthyes

Osteichthyes
Taxon Species Location Stratigraphic position Material Notes Images
Albula A. sp. Tooth plates and dentaries A species of bonefish
Characiformes indet. Partial jaw
Coelodus C. sp. A tooth plate A species of pycnodontid
Cypriniformes?
Dipnoi indet. Masorobe and Anembalemba Members Burrows
Egertonia E. sp. Partial toothplates
Enchodus E. sp. Teeth
Lepisosteus L. sp. Scales, fin rays, teeth, vertebrae, skull bones A type of gar
Paralbula P. sp. Lac Kinkony Member Partial tooth plates A species of bonefish
Sciaenidae indet. A species of croaker
Siluriformes indet. Vertebrae A type of catfish
Vango V. fahiny Lac Kinkony Member Referred material is hyomandibulae, although other partial remains of gonorynchiform probably belongs to this taxa as well A chanid gonorynchiform, milkfish

Amphibians

Amphibians
Genus Species Location Stratigraphic position Material Notes Images
Beelzebufo Beelzebufo ampinga locality MAD98-25 A large frog

Dinosaurs

Indeterminate Lithostrotia remains formerly attributed to Titanosauridae. Undescribed Lithostrotia form. Indeterminate Enantiornithes remains. A rich avifauna with several undescribed taxa are known, including pengornithid enantiornithes and putative omnivoropterygids.

Ornithischians

Ornithischians of the Maevarano Formation
Genus Species Location Stratigraphic position Material Notes Images
Stegosaurus S. madagascariensis "Teeth" An indeterminate thyreophoran.

Sauropods

Sauropods of the Maevarano Formation
Genus Species Location Stratigraphic position Material Notes Images
Rapetosaurus R. krausei "[Three] skulls, at least [one] postcranial skeleton." A titanosaur
Titanosaurus T. madagascariensis
Vahiny V. depereti "Partial braincase" A titanosaur

Theropods

Theropods of the Maevarano Formation
Genus Species Location Stratigraphic position Material Notes Images
Falcatakely F. forsterae "Partial skull" A member of Enantiornithes
Majungasaurus M. crenatissimus "Scattered remains leading to nearly most of the animal." An abelisaur
Masiakasaurus M. knopfleri "Disarticulated remains of at least 6 individuals," as well as other isolated fossils. A noasaurid abelisaur
Rahonavis R. ostromi "Partial postcranial skeleton" A paravian of unclear phylogenetic placement
Vorona V. berivotrensis "Partial hindlimbs" An ornithuromorph

Crocodylomorphs

Crocodylomorphs
Genus Species Location Stratigraphic position Material Notes Images
Mahajangasuchus M. insignis disarticulated postcranial skeleton, multiple skull remains A mahajangasuchid
Miadanasuchus M. oblita A peirosaurid. Formerly known as Trematochampsa oblita
Simosuchus S. clarki multiple specimens representing most of the skeleton A ziphosuchian
Araripesuchus A. tsangatsangana Anembalemba Member multiple specimen including several skulls and one almost complete specimen A notosuchian

Squamates

Squamates
Genus Species Location Stratigraphic position Material Notes Images
Adinophis A. fisaka A madtsoiid snake
Indophis I. fanambinana A nigerophid snake
Kelyophis K. hechti A nigerophiid snake
Konkasaurus K. mahalana A cordylid lizard
Madtsoia M. madagascariensis A madtsoiid snake
Menarana M. nosymena Vertebrae and rib fragments A madtsoiid snake

Turtles

Turtles
Genus Species Location Stratigraphic position Material Notes Images
Kinkonychelys K. rogersi A side-necked turtle
Sahonachelys S. mailakavava A sahonachelyid side-necked turtle
Sokatra S. antitra A sahonachelyid side-necked turtle

Mammals

Mammal remains include an undescribed gondwanathere, a broken tooth UA 8699, which has been interpreted both as metatherian and as eutherian, a non-gondwanathere multituberculate tooth fragment, a non-gondwanathere multituberculate femur, and a yet undescribed mammal known from an articulated skeleton. Some taxa are particularly large sized herbivores, exemplifying the diversity of Mesozoic mammals.

Mammals
Genus Species Location Stratigraphic position Material Notes Images
Adalatherium A. hui A gondwanatherian
Lavanify L. miolaka teeth A gondwanatherian
Vintana V. sertichi A gondwanatherian

See also

References

  1. ^ Rogers et al., 2007
  2. ^ Weishampel et al., 2004
  3. ^ Krause et al., 2007b
  4. ^ Depéret, 1896
  5. ^ Sues & Taquet, 1979
  6. ^ Evans, Susan E.; Jones, Marc E. H.; Krause, David W. (2008). "A giant frog with South American affinities from the Late Cretaceous of Madagascar". Proceedings of the National Academy of Sciences of the United States of America. 105 (8): 2951–2956. Bibcode:2008PNAS..105.2951E. doi:10.1073/pnas.0707599105. PMC 2268566. PMID 18287076.
  7. ^ Roberts, E.M.; Rogers, R.R.; Foreman, B.Z. (2007). "Continental insect borings in dinosaur bone: Examples from the late Cretaceous of Madagascar and Utah". Journal of Paleontology. 81 (1): 201–208. doi:10.1666/0022-3360(2007)81[201:CIBIDB]2.0.CO;2. S2CID 130016402.
  8. ^ Stigall, A.L.; Hartman, J.H. (2008). "A New Spinicaudatan Genus (Crustacea: 'Conchostraca') from the Late Cretaceous of Madagascar". Palaeontology. 51 (5): 1053–1067. Bibcode:2008Palgy..51.1053S. doi:10.1111/j.1475-4983.2008.00799.x. S2CID 86393912.
  9. ^ Ostrowski, S.A. (2012). "The teleost ichthyofauna from the Late Cretaceous of Madagascar: systematics, distributions, and implications for Gondwanan biogeography" (PDF). Michigan State University. Geological Sciences.
  10. ^ Marshall, M.S.; Rogers, R.R. (2013). "Lungfish Burrows from the Upper Cretaceous Maevarano Formation, Mahajanga Basin, Northwestern Madagascar". PALAIOS. 27 (12): 857–866. Bibcode:2013Palai..27..857M. doi:10.2110/palo.2012.p12-018r. S2CID 128912046.
  11. ^ Gottfried, M.D.; Krause, D.W. (1998). "First record of gars (Lepisosteidae, Actinopterygii) on Madagascar: Late Cretaceous remains from the Mahajanga Basin". Journal of Vertebrate Paleontology. 18 (2): 275–279. Bibcode:1998JVPal..18..275G. doi:10.1080/02724634.1998.10011056. JSTOR 4523898.
  12. ^ Murray, Alison M.; Brinkman, Donald B.; Friedman, Matt; Krause, David W. (2023-10-17). "A large, freshwater chanid fish (Ostariophysi: Gonorynchiformes) from the Upper Cretaceous of Madagascar". Journal of Vertebrate Paleontology. doi:10.1080/02724634.2023.2255630. ISSN 0272-4634.
  13. ^ Evans et al., 2014, p.5
  14. ^ O'Connor and Forster, 2010. A Late Cretaceous (Maastrichtian) avifauna from the Maevarano Formation, Madagascar. Journal of Vertebrate Paleontology. 30(4), 1178-1201.
  15. ^ "83.2 Faritany Majunga, Madagascar; 3. Maevarano Formation," in Weishampel et al., 2004, p.605
  16. ^ "Table 14.1," in Weishampel, et al. (2004). Page 326.
  17. ^ Maidment, Susannah; Norman, David; Barrett, Paul; Upchurch, Paul (2008). "Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia)". Journal of Systematic Palaeontology. 6 (4): 367–407. Bibcode:2008JSPal...6..367M. doi:10.1017/S1477201908002459. S2CID 85673680.
  18. ^ "Table 13.1," in Weishampel, et al. (2004). Page 270.
  19. ^ Rogers & Wilson, 2014
  20. ^ Patrick M. O’Connor; Alan H. Turner; Joseph R. Groenke; Ryan N. Felice; Raymond R. Rogers; David W. Krause; Lydia J. Rahantarisoa (2020). "Late Cretaceous bird from Madagascar reveals unique development of beaks". Nature. 588 (7837): 272–276. Bibcode:2020Natur.588..272O. doi:10.1038/s41586-020-2945-x. PMID 33239782. S2CID 227174405.
  21. ^ "Table 3.1," in Weishampel et al., 2004, p.50
  22. ^ "Table 3.1," in Weishampel et al., 2004, p.49
  23. ^ "Table 11.1," in Weishampel et al., 2004, p.211
  24. ^ "Table 11.1," in Weishampel et al., 2004, p.212
  25. ^ Krause et al, 2014
  26. ^ Krause, David W.; Hoffmann, Simone; Werning, Sarah (December 2017). "First postcranial remains of Multituberculata (Allotheria, Mammalia) from Gondwana". Cretaceous Research. 80: 91–100. Bibcode:2017CrRes..80...91K. doi:10.1016/j.cretres.2017.08.009.
  27. ^ Krause, David W.; O'Connor, Patrick M.; Rogers, Kristina Curry; Sampson, Scott D.; Buckley, Gregory A.; Rogers, Raymond R. (23 August 2006). "Late Cretaceous terrestrial vertebrates from Madagascar: Implications for Latin American biogeography". Annals of the Missouri Botanical Garden. 93 (2): 178–208. doi:10.3417/0026-6493(2006)93[178:LCTVFM]2.0.CO;2. JSTOR 40035721. S2CID 9166607.
  28. ^ Krause et al., 2020

Bibliography

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