Mimodactylus

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Mimodactylus
Temporal range: Late Cretaceous, 95 
Ma
↓
Holotype specimen with interpretive drawing and inset close-ups of the scapula and coracoid (b), wrist (c), and humerus
(d)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Order: †Pterosauria
Suborder: †Pterodactyloidea
Clade: †
Istiodactyliformes
Clade: †Mimodactylidae
Genus: †Mimodactylus
Kellner et al., 2019
Species:
†M. libanensis
Binomial name
†Mimodactylus libanensis
Kellner et al., 2019

Mimodactylus is a

holotype specimen is the first complete pterosaur from the Afro-Arabian continent (which consisted of the then joined Arabian Peninsula and Africa
), and the third pterosaur fossil known from Lebanon.

The holotype specimen is comparatively small, with a wingspan of 1.32 metres (4.3 ft), and was probably a young individual. Its snout is broad and the cone-shaped teeth are confined to the front half of the jaws. The

Neotethys
ocean at the time, but some small islands were exposed.

History of discovery

Map showing Hjoula (a-b) and position of Lebanon during the late Cenomanian (c)

The only known specimen of this

palaeocontinent) is generally very limited, with only South Africa having been systematically studied.[1][2][3][4][5]

The very fragile but well-preserved pterosaur specimen was split in two pieces when discovered on the limestone

Saint Joseph University of Beirut, so that it could be kept in Lebanon.[1][2][3]

Skeletal diagram; the scale bar is 50 mm (2.0 in)

The Canadian palaeontologists Michael W. Caldwell and

Alexander W. A. Kellner, Borja Holgado, and Juliana M. Sayão, Italian Fabio M. Dalla Vecchia, and Lebanese Roy Nohra (Kellner and Dalla Vecchia had previously done fieldwork in Lebanon together). In interviews, the researchers expressed pleasure in the specimen being returned to Lebanon, where it can be used for education and research, and in having the opportunity to collaborate internationally. In 2019, Kellner and colleagues named the new genus and species Mimodactylus libanensis; the generic name refers to the MIM Museum, in recognition of where the specimen is housed and according to the wishes of the philanthropist who acquired the specimen, combined with the Greek word daktylos (δάκτυλος) for "digit". The specific name refers to Lebanon.[1][2][3][6]

The

hologram, a movie, a life-sized reconstruction, and a game.[7][3]

Description

The only known Mimodactylus specimen is comparatively small, with a wingspan of 1.32 metres (4.3 ft). It was probably a young individual when it died, based on some bones not being fused; the

sparrow, a head longer than its body, and being rather like "wings with a mouth".[3]

Skull

Skull and jaws, with inset close-up of the upper front teeth

The preserved part of the skull of Mimodactylus is 99 mm (3.9 in) long, and the preserved part of the lower jaw is 105 mm (4.1 in). The

istiodactyliforms, the group they both belonged to. The upper jaws have eleven cone-shaped teeth on each side, and the lower jaws have ten on each side, and the teeth are confined to the front half of the jaws, as in the related Haopterus and Linlongopterus. A similar configuration is also seen in other istiodactyliforms.[1]

The

tooth crowns are compressed sideways and have a cingulum (a thickened ridge at the crown base), as in Haopterus and other istiodactyliforms. A cingulum is also known from the teeth of istiodactylids and related pterosaurs, but these have wide crowns, which are also compressed sideways. Mimodactylus does not have the lancet-shaped teeth with sideways compressed crowns which are characteristic of istiodactylids, though, and also lacks the sharp carinae (cutting edges) seen in Istiodactylus. The first upper tooth of Mimodactylus is small, with an almost circular cross-section, and the following teeth are the largest of the upper jaw, and have slightly sideways compressed crowns with a cingulum, convex outer surfaces, and thin, needle-like tips which are inclined inwards.[1]

Mimodactylus's dentition is similar to that of more

hyoid (tongue bone) are thin, elongated, and fork-shaped.[1]

Postcranial skeleton

dorsal vertebrae of the back near the right scapula and coracoid

The front

shoulder-girdle). The coracoid is 31 mm (1.2 in) long. The articulation between the coracoid and the sternum is slightly concave as in Haopterus, with a backward protrusion that is not seen in istiodactylids.[1][11]

caudal vertebrae
of the tail

The

phalanx bones of the wing-finger; the humerus is unique in being less than half the length of the second phalanx. The first wing phalanx is 128 mm (5.0 in) long, the second 119 mm (4.7 in), the third 105 mm (4.1 in), and the fourth 92 mm (3.6 in). The outer part of the wing-finger's last phalanx is curved, as in most pterosaurs.[1]

The pteroid bone (a hand-bone unique to pterosaurs which supported the front wing-membrane or propatagium) of Mimodactylus is rather large, and longer than the humerus at 53 mm (2.1 in). The pteroid clearly articulated with the proximal syncarpal and pointed towards the body; the position of the pteroid in pterosaurs had been a point of contention among researchers, but was settled due to the perfect articulation of the forelimbs in Mimodactylus. The humerus is much longer than the femur (thighbone), the preserved part of which is 36 mm (1.4 in) long. The tibiotarsus (lower-leg bone) is 60 mm (2.4 in) long. As in istiodactylids, the feet are relatively small. The exact combination of its various anatomical features also distinguishes Mimodactylus from other ornithocheiroids.[1]

Classification

In their 2019

Istiodactyliformes. They excluded the possibly related Linlongopterus from their analysis for being a "wildcard taxon" (of uncertain placement that changes between analyses). They noted that Mimodactylus is the first istiodactyliform known from Gondwana (the southern supercontinent which included Africa and Arabia), members of the group previously being only known from Early Cretaceous sites in Europe and Asia.[1]

Teeth (above) compared to those of the related Haopterus

The cladogram below shows the position of Mimodactylus and Mimodactylidae within Istiodactyliformes according to Kellner and colleagues, 2019:[1]

Pteranodontoidea

A 2021 study by the Chinese paleontologist Jiang Shunxing and colleagues found Mimodactylus in a

sister taxon of Linlongopterus in 2022, with Haopterus at the base of their clade.[13] The American palaeontologist Gregory S. Paul considered Yixianopterus part of Mimodactylidae in 2022.[9] A 2023 article by the British paleontologist Steven C. Sweetman noted that Mimodactylus was the latest occurring member of Istiodactyliformes.[14]

Palaeobiology

Feeding and diet

Life restoration of Mimodactylus in its environment, by Julius Csotonyi

As they have no modern

exoskeletons of arthropods.[1]

Extant vertebrate animals that feed on insects while flying have short wings with low

crustaceans from water surfaces, similar to how some albatrosses feed on shrimp.[1] The broad rostrum and widely spaced, relatively robust, and pointed teeth of Mimodactylus would have been helpful for seizing shrimp in the water.[1]

Insects had not been discovered at Hjoula or the other Cretaceous Lagerstätten of Lebanon by the time Mimodactylus was described, and fossils of terrestrial plants are very rare at Hjoula. This indicated to Kellner and colleagues that the area was very far from land, and the continent several hundreds of kilometres away. They stated that Mimodactylus lived in

boat-billed herons, and shoebills. They concluded that this expanded the spectrum of feeding strategies known in derived pterodactyloid pterosaurs.[1]

crustaceans

The first two fossil

taphonomic bias in favour of preserving strong fliers. These researchers stated that although the Hjoula outcrop represents a marine environment, fossils of terrestrial organisms (including the then newly discovered insects and pterosaurs) indicate they were deposited close to a shoreline during the early late Cenomanian.[4] More insects have since been discovered in Hjoula, supporting the idea that the area was close to the shore at the time.[15][16]

Palaeoenvironment

Fossil of Libanopristis, a genus of ray known from Hjoula

Mimodactylus is known from the Sannine Formation in Hjoula, Lebanon, which is dated to the late Cenomanian age of the Late Cretaceous, about 95 million years ago. This age was determined via biostratigraphy, by comparing with fossils from localities elsewhere in the world whose dates are known. Lebanon was mostly submerged on a large, shallow carbonate platform during the middle Cenomanian, which bordered the northeastern part of the Afro-Arabian continent with the Neotethys ocean, but some small islands were exposed. Deposits of the Hjoula outcrops are marine, but terrestrial fossils indicate that it was close to a palaeoshore during the late Cenomanian.[1][4] The limestone of Hajoula is compact, soft, and laminated rock, which is characterised by being light yellow or grey-yellow in colour, and in not having flint nodules.[17]

The Cenomanian

Octopuses include Keuppia and Styletoctopus.[17] Many of the fossil taxa found in Hjoula are also found in the Hakel locality of the same age.[1][23][19]

See also

References

  1. ^
    PMID 31784545
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  2. ^ a b c "Pterosaur flies safely home after 95 million years". The Archaeology News Network. 2016. Archived from the original on August 25, 2022. Retrieved 3 August 2023.
  3. ^ a b c d e Bartko, Karen (2019). "New kind of pterodactyl uncovered with help from U of A paleontologist". Global News. Retrieved 3 August 2023.
  4. ^
    S2CID 134308438
    .
  5. ^ Capasso, Luigi (2017). "The history and the situation of the world famous fossil fish quarries in Lebanon". Bollettino del Museo Civico di Storia Naturale di Verona. 41: 53–76.
  6. ^ a b Sousa, Thais (2019). "Brazilians find new species of flying reptile in Lebanon". Agência de Notícias Brasil-Árabe. Retrieved 24 July 2023.
  7. ^ "Interactive map of MIM - Pterosaur Area". www.mim.museum. Retrieved 24 July 2023.
  8. PMID 26131631
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  9. ^
    ISBN 9780691180175
    .
  10. ^
    ISBN 978-0-691-15061-1
    .
  11. S2CID 258273168
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  12. ISSN 2096-9899
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  13. PMID 35910775
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  14. doi:10.1016/j.cretres.2023.105622
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  15. ^
    S2CID 253513442
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  16. S2CID 237877058
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  17. ^
    S2CID 129082916
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  18. S2CID 128405107
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  19. ^ a b Hay, Oliver P. (1903). "On a collection of Upper Cretaceous fishes from Mount Lebanon, Syria, with descriptions of four new genera and nineteen new species". Bulletin of the American Museum of Natural History. 19: 395–452.
  20. ^ Capasso, Luigi L.; Abi Saad, Pierre; Taverne, Louis (2009). "Nursallia tethysensis sp. nov., a new pycnodont fish (Neopterygii: †halecostomi) from the Cenomanian of Lebanon". Bulletin de l'Institut Royal des Sciences Naturelles de Belqique, Sciences de la Terre. 79: 117–136.
  21. ISSN 2748-8721
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  22. doi:10.11646/palaeoentomology.5.2.8
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  23. ^ a b Garassino, Alessandro (1994). "The macruran decapod crustaceans of the Upper Creataceous of Lebanon". Paleontologia Lombarda. III: 5.
  24. PMID 26319267
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External links

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