Kryptops
{{Short description|Extinct genus of dinosaurs}}
{{automatic taxobox
| fossil_range = Early Cretaceous, {{fossil range|115|110}}
| image = Kryptops skeletal diagram.jpg
| image_caption = Skeletal diagram showing the only known bone, a {{Dinogloss|maxilla}} (upper jaw bone); the other remains shown are now thought to belong to a different species.
| taxon = Kryptops
| authority = Sereno & Brusatte, 2008
| type_species = {{extinct}}Kryptops palaios
| type_species_authority = Sereno & Brusatte, 2008
| subdivision_ranks =
| subdivision =
}}
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 {{gloss|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 {{gloss|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 {{cvt|6|-|7|m|1}}, 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
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.{{Cite web |last=Koppes |first=Steve |date=2000 |title=Dinosaur Expedition 2000 allows us to join team in Niger |url=https://chronicle.uchicago.edu/001102/sereno-in-niger.shtml |access-date=2025-03-21 |website=chronicle.uchicago.edu}}{{Cite web |last=Anonymous |title=Huge fossil crocodilian discovered |url=https://www.ntxe-news.com/cgi-bin/artman/exec/view.cgi?archive=3&num=9241 |access-date=2025-03-21 |website=North Texas e-News}} 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 {{Convert|15|m|ft}} away from a set of {{Dinogloss|postcranial}} elements consisting of three dorsal (back) vertebrae, two ribs, the {{Dinogloss|sacrum}}, and the {{Dinogloss|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.
File:Paul Sereno Lab Photo (cropped).jpg, 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.{{Cite journal |last1=Sereno |first1=Paul C. |last2=Wilson |first2=Jeffrey A. |last3=Conrad |first3=Jack L. |date=2004-07-07 |title=New dinosaurs link southern landmasses in the Mid–Cretaceous |journal=Proceedings of the Royal Society of London. Series B: Biological Sciences |volume=271 |issue=1546 |pages=1325–1330 |doi=10.1098/rspb.2004.2692 |pmc=1691741 |pmid=15306329}} 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 {{langx|grc|krypto}} {{gloss|covered}} and {{langx|grc|ops}} {{gloss|face}}, both in reference to the unique anatomy of the maxilla. The species name {{lang|grc|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.{{cite journal |last1=Sereno |first1=Paul C. |last2=Brusatte |first2=Stephen L. |year=2008 |title=Basal abelisaurid and carcharodontosaurid theropods from the Lower Cretaceous Elrhaz Formation of Niger |url=http://www.app.pan.pl/archive/published/app53/app53-015.pdf |journal=Acta Palaeontologica Polonica |volume=53 |issue=1 |pages=15–46 |doi=10.4202/app.2008.0102 |doi-access=free |authorlink=Paul Sereno |authorlink2=Stephen L. Brusatte}}{{Cite web |last=Mortimer |first=Mickey |date=2024 |title=Phylogeny of Taxa |url=https://theropoddatabase.github.io/Phylogeny%20of%20Taxa.html |access-date=2025-03-24 |website=theropoddatabase.github.io}}
= Identity of postcranial material =
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.{{Cite journal |last=Sereno |first=Paul C. |date=2017 |title=Early Cretaceous Ornithomimosaurs (Dinosauria: Coelurosauria) from Africa |url=http://www.bioone.org/doi/10.5710/AMGH.23.10.2017.3155 |journal=Ameghiniana |language=en |volume=54 |issue=5 |pages=576–616 |doi=10.5710/AMGH.23.10.2017.3155 |bibcode=2017Amegh..54..576S |issn=0002-7014}} 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.{{cite journal |last1=Carrano |first1=Matthew T. |last2=Benson |first2=Roger B. J. |last3=Sampson |first3=Scott D. |year=2012 |title=The phylogeny of Tetanurae (Dinosauria: Theropoda) |journal=Journal of Systematic Palaeontology |volume=10 |issue=2 |pages=211–300 |bibcode=2012JSPal..10..211C |doi=10.1080/14772019.2011.630927 |s2cid=85354215}} However, there is no overlap with the Eocarcharia holotype, which consists only of skull elements.{{Cite journal |last1=Kellermann |first1=Maximilian |last2=Cuesta |first2=Elena |last3=Rauhut |first3=Oliver W. M. |date=2025-01-14 |title=Re-evaluation of the Bahariya Formation carcharodontosaurid (Dinosauria: Theropoda) and its implications for allosauroid phylogeny |journal=PLOS ONE |language=en |volume=20 |issue=1 |pages=e0311096 |doi=10.1371/journal.pone.0311096 |doi-access=free |issn=1932-6203 |pmc=11731741 |pmid=39808629|bibcode=2025PLoSO..2011096K }} This hypothesis has been supported by later studies,{{Cite journal |last1=Novas |first1=Fernando E. |last2=Agnolín |first2=Federico L. |last3=Ezcurra |first3=Martín D. |last4=Porfiri |first4=Juan |last5=Canale |first5=Juan I. |date=2013-10-01 |title=Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia |url=https://www.sciencedirect.com/science/article/abs/pii/S0195667113000608 |journal=Cretaceous Research |volume=45 |pages=174–215 |doi=10.1016/j.cretres.2013.04.001 |bibcode=2013CrRes..45..174N |hdl=11336/102037 |issn=0195-6671|hdl-access=free }}{{Cite journal |last1=Farke |first1=Andrew A. |last2=Sertich |first2=Joseph J. W. |date=2013-04-18 |title=An Abelisauroid Theropod Dinosaur from the Turonian of Madagascar |journal=PLOS ONE |language=en |volume=8 |issue=4 |pages=e62047 |doi=10.1371/journal.pone.0062047 |doi-access=free |issn=1932-6203 |pmc=3630149 |pmid=23637961|bibcode=2013PLoSO...862047F }} though researcher Andrea Cau, in 2024, suggested that the assigned postcranial material may instead belong to the family Metriacanthosauridae.{{Cite journal |last=Cau |first=A. |year=2024 |title=A Unified Framework for Predatory Dinosaur Macroevolution |url=https://www.researchgate.net/publication/379902868 |journal=Bollettino della Società Paleontologica Italiana |volume=63 |issue=1 |doi=10.4435/BSPI.2024.08 |doi-broken-date=2024-11-20}} [https://www.paleoitalia.it/bollettino-spi/bspi-vol-631/ Supplementary Material] 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.{{Cite journal |last=Delcourt |first=Rafael |date=2018-06-27 |title=Ceratosaur palaeobiology: new insights on evolution and ecology of the southern rulers |journal=Scientific Reports |language=en |volume=8 |issue=1 |pages=9730 |doi=10.1038/s41598-018-28154-x |pmid=29950661 |pmc=6021374 |bibcode=2018NatSR...8.9730D |issn=2045-2322}}{{Cite journal |last1=Zaher |first1=Hussam |last2=Pol |first2=Diego |last3=Navarro |first3=Bruno A. |last4=Delcourt |first4=Rafael |last5=Carvalho |first5=Alberto B. |date=2020 |title=An Early Cretaceous theropod dinosaur from Brazil sheds light on the cranial evolution of the Abelisauridae |url=https://ri.conicet.gov.ar/handle/11336/153682 |journal=PaleoVol |issue=6 |doi=10.5852/cr-palevol2020v19a6 |issn=1631-0683|hdl=11336/153682 |hdl-access=free }} This viewpoint has been supported by some other authors, though a detailed reanalysis of the genus has not been done.
Description
File:Kryptops size chart.jpgThe holotype individual is large, belonging to an adult about {{cvt|6|-|7|m|1}} 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 {{Convert|15|cm|in}} and is missing the distal portion of the {{Dinogloss|ramus}}, some of the {{Dinogloss|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, {{Dinogloss|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.{{Cite journal |last1=Cerroni |first1=M.A. |last2=Canale |first2=J. I. |last3=Novas |first3=F. E. |date=2021-10-03 |title=The skull of Carnotaurus sastrei Bonaparte 1985 revisited: insights from craniofacial bones, palate and lower jaw |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2020.1802445 |journal=Historical Biology |volume=33 |issue=10 |pages=2444–2485 |bibcode=2021HBio...33.2444C |doi=10.1080/08912963.2020.1802445 |issn=0891-2963 |via=M.A. Cerroni}}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. 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. There is a row of neurovascular {{Dinogloss|foramina}} located above the alveolar margin, a characteristic of abelisauroids.
File:Kryptops life restoration.jpg
Its maxilla arches medially towards the articulation with the {{Dinogloss|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. The {{Dinogloss|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. Dorsal and ventral edges of the {{Dinogloss|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 {{Dinogloss|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 {{Convert|5|mm|in}}. This is comparable to the serration counts of indeterminate abelisaurids from Morocco and Egypt but greater than that of Rugops.
Classification
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,{{Cite journal |last=Hendrickx |first=Christophe |last2=Mateus |first2=Octávio |date=2014-01-30 |title=Abelisauridae (Dinosauria: Theropoda) from the Late Jurassic of Portugal and dentition-based phylogeny as a contribution for the identification of isolated theropod teeth |url=https://mapress.com/zt/article/view/zootaxa.3759.1.1 |journal=Zootaxa |language=en |volume=3759 |issue=1 |pages=1–74 |doi=10.11646/zootaxa.3759.1.1 |issn=1175-5334}}{{Cite journal |last=Pol |first=Diego |last2=Rauhut |first2=Oliver W. M. |date=2012-05-23 |title=A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs |url=https://royalsocietypublishing.org/doi/10.1098/rspb.2012.0660 |journal=Proceedings of the Royal Society B: Biological Sciences |volume=279 |issue=1741 |pages=3170–3175 |doi=10.1098/rspb.2012.0660 |pmc=3385738 |pmid=22628475}} up until the Cretaceous-Paleogene extinction event.{{Cite journal |last=Longrich |first=Nicholas R. |last2=Pereda-Suberbiola |first2=Xabier |last3=Jalil |first3=Nour-Eddine |last4=Khaldoune |first4=Fatima |last5=Jourani |first5=Essaid |date=2017-08-01 |title=An abelisaurid from the latest Cretaceous (late Maastrichtian) of Morocco, North Africa |url=https://linkinghub.elsevier.com/retrieve/pii/S0195667116303706 |journal=Cretaceous Research |volume=76 |pages=40–52 |doi=10.1016/j.cretres.2017.03.021 |issn=0195-6671}} Abelisaurids have been recovered as the sister family to the noasaurids within the superfamily Abelisauroidea.{{Cite journal |last=Rauhut |first=Oliver W. M. |last2=Carrano |first2=Matthew T. |date=2016-11-01 |title=The theropod dinosaur Elaphrosaurus bambergi Janensch, 1920, from the Late Jurassic of Tendaguru, Tanzania |url=https://academic.oup.com/zoolinnean/article-abstract/178/3/546/2667468?redirectedFrom=fulltext |journal=Zoological Journal of the Linnean Society |volume=178 |issue=3 |pages=546–610 |doi=10.1111/zoj.12425 |issn=0024-4082}} 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. 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, though it has been included in a few published cladograms.{{Cite journal |last=Gianechini |first=Federico A. |last2=Apesteguía |first2=Sebastián |last3=Landini |first3=Walter |last4=Finotti |first4=Franco |last5=Juárez Valieri |first5=Rubén |last6=Zandonai |first6=Fabiana |date=2015-05-01 |title=New abelisaurid remains from the Anacleto Formation (Upper Cretaceous), Patagonia, Argentina |url=https://www.sciencedirect.com/science/article/abs/pii/S0195667114002201 |journal=Cretaceous Research |volume=54 |pages=1–16 |doi=10.1016/j.cretres.2014.11.009 |issn=0195-6671|hdl=11336/37727 |hdl-access=free }} 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.{{Cite journal |last=Hendrickx |first=Christophe |last2=Cerroni |first2=Mauricio A |last3=Agnolín |first3=Federico L |last4=Catalano |first4=Santiago |last5=Ribeiro |first5=Cátia F |last6=Delcourt |first6=Rafael |date=2024-12-01 |title=Osteology, relationship, and feeding ecology of the theropod dinosaur Noasaurus lealiBonaparte and Powell, 1980, from the Late Cretaceous of North-Western Argentina |url=https://academic.oup.com/zoolinnean/article-abstract/202/4/zlae150/7926352?redirectedFrom=fulltext |journal=Zoological Journal of the Linnean Society |volume=202 |issue=4 |pages=zlae150 |doi=10.1093/zoolinnean/zlae150 |issn=0024-4082}} Below is the phylogenetic analysis conducted during the description of Viavenator in 2016:{{Cite journal |last1=Filippi |first1=Leonardo S. |last2=Méndez |first2=Ariel H. |last3=Juárez Valieri |first3=Rubén D. |last4=Garrido |first4=Alberto C. |date=2016-06-01 |title=A new brachyrostran with hypertrophied axial structures reveals an unexpected radiation of latest Cretaceous abelisaurids |url=https://www.sciencedirect.com/science/article/abs/pii/S0195667115301439 |journal=Cretaceous Research |volume=61 |pages=209–219 |doi=10.1016/j.cretres.2015.12.018 |bibcode=2016CrRes..61..209F |hdl=11336/149906 |issn=0195-6671|hdl-access=free }}{{clade|1={{clade
|1=Kryptops
|2={{clade
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|1=Rugops
|2={{clade
|1={{clade
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|1={{clade
|1=Dahalokely
}}
|2={{clade
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|1=Ilokelesia
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|2=Ekrixinatosaurus }} }}
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}} }} }} }} }} }} }} }}
|style=font-size: 100%; line-height:100%|label1=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.
Palaeoenvironment
File:Gadoufaoua.png 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.{{Cite journal |last1=Sereno |first1=Paul C. |last2=Beck |first2=Allison L. |last3=Dutheil |first3=Didier B. |last4=Larsson |first4=Hans C. E. |last5=Lyon |first5=Gabrielle H. |last6=Moussa |first6=Bourahima |last7=Sadleir |first7=Rudyard W. |last8=Sidor |first8=Christian A. |last9=Varricchio |first9=David J. |last10=Wilson |first10=Gregory P. |last11=Wilson |first11=Jeffrey A. |date=1999-11-12 |title=Cretaceous Sauropods from the Sahara and the Uneven Rate of Skeletal Evolution Among Dinosaurs |url=https://www.science.org/doi/10.1126/science.286.5443.1342 |journal=Science |volume=286 |issue=5443 |pages=1342–1347 |doi=10.1126/science.286.5443.1342}} The sediments are coarse- to medium-grained, with almost no fine-grained horizons. Nigersaurus lived in what is now Niger about 120 to 112 million years ago, during the Aptian and Albian ages of the mid-Cretaceous. It likely lived in habitats dominated by inland floodplains (a riparian zone).{{Cite journal |last1=Sereno |first1=Paul C. |last2=Wilson |first2=Jeffrey A. |last3=Witmer |first3=Lawrence M. |last4=Whitlock |first4=John A. |last5=Maga |first5=Abdoulaye |last6=Ide |first6=Oumarou |last7=Rowe |first7=Timothy A. |date=2007-11-21 |title=Structural Extremes in a Cretaceous Dinosaur |journal=PLOS ONE |language=en |volume=2 |issue=11 |pages=e1230 |doi=10.1371/journal.pone.0001230 |doi-access=free |issn=1932-6203 |pmc=2077925 |pmid=18030355|bibcode=2007PLoSO...2.1230S }}
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.{{cite journal |last1=Sereno |first1=Paul C. |date=2017 |title=Early Cretaceous Ornithomimosaurs (Dinosauria: Coelurosauria) from Africa |journal=Ameghiniana |volume=54 |issue=5 |pages=576–616 |doi=10.5710/AMGH.23.10.2017.3155|bibcode=2017Amegh..54..576S }}
See also
{{Portal|Dinosaurs}}
References
{{Reflist}}
{{Theropoda|B.}}
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Category:Early Cretaceous dinosaurs of Africa
Category:Fossil taxa described in 2008