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Kryptops

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Kryptops
Temporal range: Early Cretaceous, 115–110 Ma
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Skeletal diagram showing the only known bone, a maxilla (upper jaw bone); the other remains shown are now thought to belong to a different species.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: †Abelisauridae
Genus: †Kryptops
Sereno & Brusatte, 2008
Type species
†Kryptops palaios
Sereno & Brusatte, 2008

Kryptops is a genus of theropod dinosaur from the Early Cretaceous of Niger. It is known from a partial maxilla (upper jaw bone) found at the Gadoufaoua locality in the western Ténéré Desert, in rocks of the Aptian–Albian-age Elrhaz Formation. The fossils were collected in 2000 by a University of Chicago expedition to Niger led by American paleontologist Paul Sereno. Following preparation and research, they were described in 2008 by Sereno and Steve Brusatte, and made the basis of a new genus and species Kryptops palaios. The genus name means 'covered face', in reference to evidence that the face bore a tightly adhering covering of keratin. The type and only known species is K. palaios, which means 'old'. Several postcranial remains were referred to the Kryptops by Sereno and Brusatte, but later studies have shown that these elements belong to a tetanuran theropod, leaving Kryptops to be only known from the incomplete maxilla.

This dinosaur has been classified as an abelisaurid, a family of medium-sized, ceratosaurian theropods that existed during the Cretaceous, and potentially Jurassic. Kryptops is one of the oldest known members of the family, making it vital to the understanding of abelisaurid evolution. Its length was estimated to be around 6–7 m (19.7–23.0 ft), making it smaller than later genera such as Carnotaurus. Kryptops was a large, carnivorous dinosaur which had highly serrated teeth, bearing many denticles, and robust upper jaws. Its maxilla's outer surface features deep striations, grooves, and rugosities, indicating that it was covered in keratin.

Discovery and naming

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Left maxilla

In 2000, an expedition conducted by the University of Chicago led by American paleontologist Paul Sereno and funded by the National Geographic Society explored fossiliferous sandstone outcrops in a site known as Gadoufaoua on the western edge of the Ténéré Desert, Niger.[1][2] These layers belong to the Elrhaz Formation, which dates to the Aptian and Albian ages of the Early Cretaceous, around 112 million years ago. During the expedition, a maxilla (main tooth-bearing bone of the upper jaw) of a theropod was collected 15 metres (49 ft) away from a set of postcranial elements consisting of three dorsal (back) vertebrae, two ribs, the sacrum, and the pelvis. These remains were then transported to the University of Chicago for study and preparation before being returned to the Musee National du Niger and deposited under the catalog number MNN GAD1. The maxilla received the catalog number MNN GAD1-1, whereas the postcranial fossils were assigned MNN GAD1-2 through MNN GAD1-8.[3]

Portrait of Paul Sereno, one of the describers of Kryptops.
Portrait of paleontologist Paul Sereno, one of the describers of Kryptops

These theropod remains were believed to belong to the same individual by Paul Sereno, who, with Jeffrey Wilson and Jack Conrad, later mentioned them in a 2004 paper as an undescribed abelisaurid.[4] Sereno and Steve Brusatte described the fossils as a new genus and species of abelisaurid, named Kryptops palaios. The generic name derives to the Ancient Greek words Ancient Greek: krypto 'covered' and Ancient Greek: ops 'face', both in reference to the unique anatomy of the maxilla. The species name palaios is from the Greek term palaios "old" in reference to the age of the fossils. The maxilla, MNN GAD1-1, was made the holotype (name-bearing) specimen of the species, and MNN GAD1-2 through MNN GAD1-8 were assigned specimens.[3][5]

Identity of postcranial material

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Sereno and Brusatte assigned the postcranial material to the same individual as the maxilla based on their close association and alleged basal abelisaurid features in the vertebrae and pelvis. Kryptops is not the only theropod known from the Elrhaz Formation; other genera include the carcharodontosaurid Eocarcharia, the possible noasaurid Afromimus, and the spinosaurid Suchomimus.[6] In 2012, Matthew Carrano and colleagues considered Kryptops palaios to be a chimera (specimen composed of multiple species), and state that its postcranial remains, especially a pelvis and sacrum, may actually belong to a carcharodontosaurid, possibly Eocarcharia.[7] However, there is no overlap with the Eocarcharia holotype, which consists only of skull elements.[8][3] This hypothesis has been supported by later studies,[9][10] though researcher Andrea Cau, in 2024, suggested that the assigned postcranial material may instead belong to the family Metriacanthosauridae.[11] The validity of Kryptops entirely came into question in 2018, when paleontologist Rafael Delcourt argued that due to the occurrence of only one valid autapomorphy (unique feature), Kryptops is a nomen dubium.[12][13] This viewpoint has been supported by some other authors,[13] though a detailed reanalysis of the genus has not been done.

Description

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Size compared to a human

The holotype individual is large, belonging to an adult about 6–7 m (19.7–23.0 ft) in length. As other abelisaurids, Kryptops had a short, deep skull attached to a long, slender body. The maxilla has a preserved tooth row length of 15 centimetres (5.9 in) and is missing the distal portion of the ramus, some of the alveolar (tooth hole) margin, and tooth crowns. The left maxilla preserved 11 alveoli (tooth positions) but likely bore 17 or 18 alveoli in total when complete based on the related genus Rugops. The exterior, lateral face of the maxilla is extremely rugose and textured, giving the genus its name. Pits and short vascular grooves adorn the surfaces, a condition similar to that of other abelisaurids and some carcharodontosaurids. This may imply a keratinous integument on the maxillae instead of scales, though the skull of Carnotaurus was scaly.[14][15] The external texture of the maxilla, with its short linear grooves, is a diagnostic characteristic of Kryptops and distinguishes it from other abelisaurids according to Sereno and Brusatte (2008). However, Delcourt, in 2018, noted that this same condition is observable in Rugops and therefore not unique to Kryptops.[12] There is a row of neurovascular foramina located above the alveolar margin, a characteristic of abelisauroids.[3]

Life restoration

Its maxilla arches medially towards the articulation with the premaxilla, resulting in a broad, short skull as in its relatives. The front section of the maxilla is short and deep, even shorter than that of other abelisaurids.[3] The proximal portion of the posterior ramus has sub-parallel dorsal (top) and ventral (bottom) margins, but these are scalloped rather than smooth, a trait unique to the genus.[12] Dorsal and ventral edges of the promaxillary fenestra are hidden in lateral view by the lateral wall of the antorbital fossa, similar to Majungasaurus, Abelisaurus, and other abelisaurids. The interdental plates are fused, textured with striations similar to the anatomy interdental plates of other abelisaurids. The medial, inner surface of the maxilla is broken, which exposes the replacement teeth. There are several complete teeth preserved within the maxilla and exposed along the tooth row. Their crowns are relatively flat and wide, as in other abelisaurids, and have about 15 serrations for every 5 millimetres (0.20 in). This is comparable to the serration counts of indeterminate abelisaurids from Morocco and Egypt but greater than that of Rugops.[3]

Classification

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The phylogenetic position of Kryptops has been unstable, as the genus is only known from a maxilla, though it probably belongs to a basal abelisaurid ceratosaur. Many phylogenetic analyses place it within Abelisauridae, a group of theropod dinosaurs that existed during the Cretaceous, though potentially Jurassic,[16][17] up until the Cretaceous-Paleogene extinction event.[18] Abelisaurids have been recovered as the sister family to the noasaurids within the superfamily Abelisauroidea.[19] In their 2008 phylogenetic analysis of the relationships of Kryptops, Sereno and Brusatte recovered Kryptops as the most basal genus of Abelisauridae at a similar grade to Rugops and Rajasaurus, far more basal than Majungasaurus and Carnotaurus.[3] This phylogenetic analysis assumed that the postcranial remains belong to Kryptops, skewing the results due to the presence of tetanuran characters. Later phylogenetic analyses excluded Kryptops due to the lack of material and its instability in phylogenetic analyses,[12][13] though it has been included in a few published cladograms.[20][21] When the postcranial material and holotype maxilla are scored separately, the postcrania is found isolated from Ceratosauria and often with Tetanurae, whereas the Kryptops is classified as a basal abelisaurid.[22] Below is the phylogenetic analysis conducted during the description of Viavenator in 2016:[20]

Abelisauridae

Kryptops, along with Rugops, is one of the earliest-known members of Abelisauridae according to several phylogenetic analyses and its age. This makes Kryptops critical to understanding the evolution and diversification of Abelisauridae. Sereno and Brusatte noted that the maxilla bore a mix of the short, robust characteristics of later Cretaceous genera in combination with primitive, still slightly elongated skull features.[3]

Palaeoenvironment

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Location of Gadoufaoua in Niger

Kryptops is known from the Elrhaz Formation of the Tegama Group in an area of the Ténéré Desert called Gadoufaoua, located in Niger. It is rare, with only one specimen definitively known. The Elrhaz Formation consists mainly of fluvial sandstones with low relief, much of which is obscured by sand dunes.[23] The sediments are coarse- to medium-grained, with almost no fine-grained horizons.[24] Nigersaurus lived in what is now Niger about 120 to 112 million years ago, during the Aptian and Albian ages of the mid-Cretaceous.[25] It likely lived in habitats dominated by inland floodplains (a riparian zone).[26]

Kryptops lived alongside the other theropods Suchomimus, Eocarcharia, and Afromimus. Several megaherbivores like the iguanodontian Lurdusaurus and sauropod Nigersaurus have been unearthed from Gadoufaoua. Other herbivores from the same formation include Ouranosaurus, Elrhazosaurus, and an unnamed titanosaur. Together, these compose one of the few associations of megaherbivores with a balance of sauropods and large ornithopods. Crocodylomorphs like Sarcosuchus, Anatosuchus, Araripesuchus, and Stolokrosuchus also lived there. In addition, remains of a pterosaur, chelonians, fish, a hybodont shark, and freshwater bivalves have been found. The aquatic fauna consists entirely of freshwater inhabitants.[3][27][26]

See also

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References

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  1. ^ Koppes, Steve (2000). "Dinosaur Expedition 2000 allows us to join team in Niger". chronicle.uchicago.edu. Retrieved 2025-03-21.
  2. ^ Anonymous. "Huge fossil crocodilian discovered". North Texas e-News. Retrieved 2025-03-21.
  3. ^ a b c d e f g h i Sereno, Paul C.; Brusatte, Stephen L. (2008). "Basal abelisaurid and carcharodontosaurid theropods from the Lower Cretaceous Elrhaz Formation of Niger" (PDF). Acta Palaeontologica Polonica. 53 (1): 15–46. doi:10.4202/app.2008.0102.
  4. ^ Sereno, Paul C.; Wilson, Jeffrey A.; Conrad, Jack L. (2004-07-07). "New dinosaurs link southern landmasses in the Mid–Cretaceous". Proceedings of the Royal Society of London. Series B: Biological Sciences. 271 (1546): 1325–1330. doi:10.1098/rspb.2004.2692. PMC 1691741. PMID 15306329.
  5. ^ Mortimer, Mickey (2024). "Phylogeny of Taxa". theropoddatabase.github.io. Retrieved 2025-03-24.
  6. ^ Sereno, Paul C. (2017). "Early Cretaceous Ornithomimosaurs (Dinosauria: Coelurosauria) from Africa". Ameghiniana. 54 (5): 576–616. Bibcode:2017Amegh..54..576S. doi:10.5710/AMGH.23.10.2017.3155. ISSN 0002-7014.
  7. ^ Carrano, Matthew T.; Benson, Roger B. J.; Sampson, Scott D. (2012). "The phylogeny of Tetanurae (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 10 (2): 211–300. Bibcode:2012JSPal..10..211C. doi:10.1080/14772019.2011.630927. S2CID 85354215.
  8. ^ Kellermann, Maximilian; Cuesta, Elena; Rauhut, Oliver W. M. (2025-01-14). "Re-evaluation of the Bahariya Formation carcharodontosaurid (Dinosauria: Theropoda) and its implications for allosauroid phylogeny". PLOS ONE. 20 (1): e0311096. Bibcode:2025PLoSO..2011096K. doi:10.1371/journal.pone.0311096. ISSN 1932-6203. PMC 11731741. PMID 39808629.
  9. ^ Novas, Fernando E.; Agnolín, Federico L.; Ezcurra, Martín D.; Porfiri, Juan; Canale, Juan I. (2013-10-01). "Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia". Cretaceous Research. 45: 174–215. Bibcode:2013CrRes..45..174N. doi:10.1016/j.cretres.2013.04.001. hdl:11336/102037. ISSN 0195-6671.
  10. ^ Farke, Andrew A.; Sertich, Joseph J. W. (2013-04-18). "An Abelisauroid Theropod Dinosaur from the Turonian of Madagascar". PLOS ONE. 8 (4): e62047. Bibcode:2013PLoSO...862047F. doi:10.1371/journal.pone.0062047. ISSN 1932-6203. PMC 3630149. PMID 23637961.
  11. ^ Cau, A. (2024). "A Unified Framework for Predatory Dinosaur Macroevolution". Bollettino della Società Paleontologica Italiana. 63 (1). doi:10.4435/BSPI.2024.08 (inactive 2024-11-20).{{cite journal}}: CS1 maint: DOI inactive as of November 2024 (link) Supplementary Material
  12. ^ a b c d Delcourt, Rafael (2018-06-27). "Ceratosaur palaeobiology: new insights on evolution and ecology of the southern rulers". Scientific Reports. 8 (1): 9730. Bibcode:2018NatSR...8.9730D. doi:10.1038/s41598-018-28154-x. ISSN 2045-2322. PMC 6021374. PMID 29950661.
  13. ^ a b c Zaher, Hussam; Pol, Diego; Navarro, Bruno A.; Delcourt, Rafael; Carvalho, Alberto B. (2020). "An Early Cretaceous theropod dinosaur from Brazil sheds light on the cranial evolution of the Abelisauridae". PaleoVol (6). doi:10.5852/cr-palevol2020v19a6. hdl:11336/153682. ISSN 1631-0683.
  14. ^ Cerroni, M.A.; Canale, J. I.; Novas, F. E. (2021-10-03). "The skull of Carnotaurus sastrei Bonaparte 1985 revisited: insights from craniofacial bones, palate and lower jaw". Historical Biology. 33 (10): 2444–2485. Bibcode:2021HBio...33.2444C. doi:10.1080/08912963.2020.1802445. ISSN 0891-2963 – via M.A. Cerroni.
  15. ^ Czerkas, Stephen A.; Czerkas, Sylvia J. (1997). "The Integument and Life Restoration of Carnotaurus". In Wolberg, D. I.; Stump, E.; Rosenberg, G. D. (eds.). Dinofest International. Academy of Natural Sciences, Philadelphia. pp. 155–158.
  16. ^ Hendrickx, Christophe; Mateus, Octávio (2014-01-30). "Abelisauridae (Dinosauria: Theropoda) from the Late Jurassic of Portugal and dentition-based phylogeny as a contribution for the identification of isolated theropod teeth". Zootaxa. 3759 (1): 1–74. doi:10.11646/zootaxa.3759.1.1. ISSN 1175-5334.
  17. ^ Pol, Diego; Rauhut, Oliver W. M. (2012-05-23). "A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs". Proceedings of the Royal Society B: Biological Sciences. 279 (1741): 3170–3175. doi:10.1098/rspb.2012.0660. PMC 3385738. PMID 22628475.
  18. ^ Longrich, Nicholas R.; Pereda-Suberbiola, Xabier; Jalil, Nour-Eddine; Khaldoune, Fatima; Jourani, Essaid (2017-08-01). "An abelisaurid from the latest Cretaceous (late Maastrichtian) of Morocco, North Africa". Cretaceous Research. 76: 40–52. doi:10.1016/j.cretres.2017.03.021. ISSN 0195-6671.
  19. ^ Rauhut, Oliver W. M.; Carrano, Matthew T. (2016-11-01). "The theropod dinosaur Elaphrosaurus bambergi Janensch, 1920, from the Late Jurassic of Tendaguru, Tanzania". Zoological Journal of the Linnean Society. 178 (3): 546–610. doi:10.1111/zoj.12425. ISSN 0024-4082.
  20. ^ a b Filippi, Leonardo S.; Méndez, Ariel H.; Juárez Valieri, Rubén D.; Garrido, Alberto C. (2016-06-01). "A new brachyrostran with hypertrophied axial structures reveals an unexpected radiation of latest Cretaceous abelisaurids". Cretaceous Research. 61: 209–219. Bibcode:2016CrRes..61..209F. doi:10.1016/j.cretres.2015.12.018. hdl:11336/149906. ISSN 0195-6671.
  21. ^ Gianechini, Federico A.; Apesteguía, Sebastián; Landini, Walter; Finotti, Franco; Juárez Valieri, Rubén; Zandonai, Fabiana (2015-05-01). "New abelisaurid remains from the Anacleto Formation (Upper Cretaceous), Patagonia, Argentina". Cretaceous Research. 54: 1–16. doi:10.1016/j.cretres.2014.11.009. hdl:11336/37727. ISSN 0195-6671.
  22. ^ Hendrickx, Christophe; Cerroni, Mauricio A; Agnolín, Federico L; Catalano, Santiago; Ribeiro, Cátia F; Delcourt, Rafael (2024-12-01). "Osteology, relationship, and feeding ecology of the theropod dinosaur Noasaurus lealiBonaparte and Powell, 1980, from the Late Cretaceous of North-Western Argentina". Zoological Journal of the Linnean Society. 202 (4): zlae150. doi:10.1093/zoolinnean/zlae150. ISSN 0024-4082.
  23. ^ Sereno, Paul C.; Beck, Allison L.; Dutheil, Didier B.; Larsson, Hans C. E.; Lyon, Gabrielle H.; Moussa, Bourahima; Sadleir, Rudyard W.; Sidor, Christian A.; Varricchio, David J.; Wilson, Gregory P.; Wilson, Jeffrey A. (1999-11-12). "Cretaceous Sauropods from the Sahara and the Uneven Rate of Skeletal Evolution Among Dinosaurs". Science. 286 (5443): 1342–1347. doi:10.1126/science.286.5443.1342.
  24. ^ Cite error: The named reference serenoetal2007 was invoked but never defined (see the help page).
  25. ^ Cite error: The named reference serenoetal1999 was invoked but never defined (see the help page).
  26. ^ a b Sereno, Paul C.; Wilson, Jeffrey A.; Witmer, Lawrence M.; Whitlock, John A.; Maga, Abdoulaye; Ide, Oumarou; Rowe, Timothy A. (2007-11-21). "Structural Extremes in a Cretaceous Dinosaur". PLOS ONE. 2 (11): e1230. Bibcode:2007PLoSO...2.1230S. doi:10.1371/journal.pone.0001230. ISSN 1932-6203. PMC 2077925. PMID 18030355.
  27. ^ Sereno, Paul C. (2017). "Early Cretaceous Ornithomimosaurs (Dinosauria: Coelurosauria) from Africa". Ameghiniana. 54 (5): 576–616. Bibcode:2017Amegh..54..576S. doi:10.5710/AMGH.23.10.2017.3155.
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