Afrocascudo

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Afrocascudo
Temporal range: Late Cretaceous (early Cenomanian), ~100–95  Ma
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Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Genus: Afrocascudo
Brito et al., 2024
Species:
A. saharaensis
Binomial name
Afrocascudo saharaensis
Brito et al., 2024

Afrocascudo is a controversial genus of extinct neopterygian fish, either an ancient loricariid catfish or a juvenile obaichthyid lepisosteiform of the genus Obaichthys . It is known from the Late Cretaceous Douira Formation (Kem Kem Group) of Morocco. The genus contains a single species, A. saharaensis, known from a partial articulated specimen.

Contents

Discovery and naming

The Afrocascudo holotype specimen, MHNM-KK-OT 36 a—c, was discovered in sediments of the Douira Formation (Jbel Oum Tkout locality) of the Kem Kem Group near Tafraoute Sidi Ali in Errachidia Province, southeastern Morocco. The articulated specimen consists of a nearly complete fish collected in three pieces. It is missing parts of the head and fins. [1]

In 2024, Brito et al. described Afrocascudo saharaensis as a new genus and species of loricariid catfishes based on these fossil remains. The generic name, Afrocascudo, combines the Latin word "Afro", meaning "Africa", with the Portuguese "cascudo", the common name used in Brazil for certain armoured catfishes. The specific name, saharaensis, references the Sahara Desert of North Africa, from which the holotype was discovered. [1]

The describers of Afrocascudo suggested that this fossil represents the oldest known catfish and, as such, the oldest known loricarioid. Before its description, the Argentinian Corydoras revelatus was the oldest known loricarioid, from the Late Paleocene (~58.5 Ma). [2] [3] The presence of a crown group loricarioid catfish in the Late Cretaceous would indicate that the clade had already significantly diversified much earlier than was previously thought. [1] This hypothesis has been disputed by other researchers who posit that the remains do not belong to a catfish. [4]

Description

Size of Afrocascudo compared to a human hand, based on the flawed initial reconstruction Afrocascudo Size Comparison.svg
Size of Afrocascudo compared to a human hand, based on the flawed initial reconstruction

Afrocascudo was a small fish, with an estimated total body length of 74 millimetres (2.9 in). About 35% of the total body length is incorporated by the head. The top and sides of the body and head are covered in odontode-coated bony plates. The skull roof is triangular, with a long, pointed snout and expanded orbit region. It had approximately 30 vertebrae in total. The distal end of the caudal fin, though not entirely preserved, seems to be symmetrically rounded with 14 rays. The dorsal fin includes a small anterior spinelet, a larger spine, and 8-9 rays. The pelvic fin has six parallel rays. [1] A physical anal fin is not preserved, and although its presence was argued by Brito et al. based on four rays allegedly observable as impressions, a later comment disputed this. [4]

Classification

In their phylogenetic analyses, Brito et al. (2024) recovered Afrocascudo within the diverse siluriform (catfish) clade Loricariidae. Loricariids—including Afrocascudo—are regarded as the "armoured catfishes", with around 1,220 extant species. Their results are displayed in the cladogram below: [1]

However, in the same year, Britz et al. considered this taxonomic placement fallacious, and reinterpreted Afrocascudo as a juvenile obaichthyid lepisosteiform, most likely an immature individual of the contemporary Obaichthys . They noted significant morphological differences between this taxon and true loriicarids, and observed that the identified traits are more similar to those of Obaichthys. Britz et al. discussed their skepticism based on the erroneous phylogenetic data matrix and reconstruction of the taxon from the previous study by Brito et al., the latter of which does not closely match the fossilized remains. They also pointed out that Brito et al. only provided the arguments in favor of their conclusion without an extensive discussion, and that their hypotheses would all be considered doubtful if Afrocascudo is considered a non-teleost fish. As such, they argued that Afrocascudo should be considered a junior synonym of Obaichthys. [4]

Shortly after the comment by Britz, Brito et al. published a rebuttal paper, acknowledging that their reconstruction took artistic liberties, proposing a possible in-life appearance for the species. They further admitted to small errors in the original study, specifically in the phylogenetic matrix and one of the figures from the supplementary data. They also concurred with Britz et al. that features of the caudal endoskeleton are not easily distinguishable. Still, they criticized Britz et al. for proposing a taxonomic status change of Afrocascudo on the basis of simple comparisons without testing hypothesis (i.e. reproducing 3D renderings), and considered the interpretation of the taxon as a juvenile lepisosteiform or a holostean unlikely. In their rebuttal, Brito et al. further claimed that Afrocascudo could not be a juvenile since the type specimen is completely ossified, an indicator for maturity. They also noted the absence of important holostean characters including the canalicules found in gar scales and the presence of teleost fish traits, such as the structure of the caudal fin, histological features, and the dorsal and lateral surfaces which are covered with bony plates and odontodes. Additionally, all principal rays of the median fins in lepisosteiforms are segmented and branched, which is different from the dorsal fin of Afrocascudo. Thus, they stood by their original conclusion that Afrocascudo represents the oldest known catfish. [5]

Paleoecology

Afrocascudo is known from the Douira Formation (Kem Kem Group) of Morocco, which dates to the Cenomanian age of the late Cretaceous period. This locality represents a fresh water environment that would have dried seasonally. Many other fossil animals have been found in similar outcrops, such as various invertebrates, other fish, [1] [6] amphibians, [7] crocodylomorphs, and dinosaurs including the large theropods Carcharodontosaurus and Spinosaurus . [8]

Related Research Articles

<span class="mw-page-title-main">Catfish</span> Order of fish

Catfish are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, the Mekong giant catfish from Southeast Asia, the wels catfish of Eurasia, and the piraíba of South America, to detritivores, and even to a tiny parasitic species commonly called the candiru, Vandellia cirrhosa. Neither the armour-plated types nor the naked types have scales. Despite their name, not all catfish have prominent barbels or "whiskers". Members of the Siluriformes order are defined by features of the skull and swimbladder. Catfish are of considerable commercial importance; many of the larger species are farmed or fished for food. Many of the smaller species, particularly the genus Corydoras, are important in the aquarium hobby. Many catfish are nocturnal, but others are crepuscular or diurnal.

<span class="mw-page-title-main">Loricariidae</span> Largest family of catfish

Loricariidae is the largest family of catfish, with over 90 genera and just over 680 species. Loricariids originate from freshwater habitats of Costa Rica, Panama, and tropical and subtropical South America. These fish are noted for the bony plates covering their bodies and their suckermouths. Several genera are sold as "plecos", notably the suckermouth catfish, Hypostomus plecostomus, and are popular as aquarium fish.

<span class="mw-page-title-main">Loricarioidea</span> Superfamily of fishes

Loricarioidea is a superfamily of catfishes. It contains the six families Trichomycteridae, Nematogenyiidae, Callichthyidae, Scoloplacidae, Astroblepidae, and Loricariidae. Some schemes also include Amphiliidae. This superfamily, including Amphiliidae, includes about 156 genera and 1,187 species.

<span class="mw-page-title-main">Diplomystidae</span> Family of fishes

Diplomystidae, the velvet catfishes, are a family of primitive catfishes endemic to freshwater habitats in Argentina and Chile in southern South America. It currently contains six species in two genera.

<i>Lasiancistrus</i> Genus of fishes

Lasiancistrus is a genus of suckermouth armored catfishes. They are native to South America and Panama.

Pseudolithoxus is a genus of suckermouth armored catfishes with five described species from the basins of the Orinoco, Casiquiare and upper Rio Negro in Venezuela. Additionally, a possibly undescribed species is known from the Trombetas and Nhamundá rivers in Brazil.

<i>Mawsonia</i> (fish) Extinct genus of coelacanths

Mawsonia is an extinct genus of prehistoric coelacanth fish. It is amongst the largest of all coelacanths, with one quadrate specimen possibly belonging to an individual measuring 5.3 metres in length. It lived in freshwater and brackish environments from the late Jurassic to the mid-Cretaceous of South America, eastern North America, and Africa. Mawsonia was first described by British paleontologist Arthur Smith Woodward in 1907.

<span class="mw-page-title-main">Kem Kem Group</span> Geological group in eastern Morocco

The Kem Kem Group is a geological group in the Kem Kem region of eastern Morocco, whose strata date back to the Cenomanian stage of the Late Cretaceous. Its strata are subdivided into two geological formations, with the lower Ifezouane Formation and the upper Aoufous Formation used for the strata on the eastern side of the Atlas Mountains (Tinghir), with the Gara Sbaa Formation and Douira Formation used in the southern Tafilalt region. It is exposed on an escarpment along the Algeria–Morocco border.

<i>Calamopleurus</i> Extinct genus of fishes

Calamopleurus is an prehistoric genus of marine holostean ray-finned fish from the Early Cretaceous of South America and northern Africa. It was a relative of the modern bowfin, with both belonging to the family Amiidae.

<i>Aphanepygus</i> Extinct genus of fishes

Aphanepygus is an extinct genus of prehistoric marine holostean ray-finned fish that lived during the upper Cenomanian. It inhabited the former Tethys Ocean, with remains known from Lebanon and Croatia. Its exact affinities are uncertain, although it is usually recovered as a relative of the macrosemiids. However, other authorities recover it in the Ionoscopiformes.

<i>Atopocephala</i> Extinct genus of fishes

Atopocephala is an extinct genus of prehistoric freshwater ray-finned fish that lived during the Middle Triassic epoch. It contains a single species, A. watsoni from the Karoo Supergroup of South Africa. A potential indeterminate species was known from the Timezgadiouine Formation of Morocco, but is now considered an indeterminate actinopterygian.

<i>Corydoras revelatus</i> Extinct species of fish

Corydoras revelatus is an extinct species of callichthyid catfish known from a single specimen found in Late Paleocene strata of the Mais Gordo Formation in Salta, Argentina. According to chronological dating of the strata, the fossil specimen is about 58.2–58.5 million years old.

<span class="mw-page-title-main">Pycnodontidae</span> Extinct family of fishes

Pycnodontidae is an extinct family of ray-finned fishes, ranging from the Jurassic period until the Eocene. It was the largest and most derived family of the successful Mesozoic fish order Pycnodontiformes, and one of only two families to survive into the Cenozoic.

Gualicho is a genus of theropod dinosaur. The type species is Gualicho shinyae. It lived in what is now northern Patagonia, on what was then a South American island continent split off from the supercontinent Gondwana. The fossils were found in the Huincul Formation, dating to the late Cenomanian-early Turonian age of the upper Cretaceous Period, around 91 million years ago.

<i>Concavotectum</i> Extinct genus of fishes

Concavotectum is an extinct genus of freshwater plethodid ray-finned fish that lived during the Cenomanian in Morocco and possibly Egypt. It was discovered and named in 2008 and is known from a single well preserved hand-sized skull and a few isolated vertebrae discovered in the Kem Kem Group. The type species, C. moroccensis, was named in 2008 and described in 2010.

Yaluwak is a genus of armored catfish native to South America where they are only known from Guyana, containing only a single species Yaluwak primus. It was first described in a 2020 study and placed within the tribe Ancistrini.

<span class="mw-page-title-main">Obaichthyidae</span> Extinct family of ray-finned fishes

Obaichthyidae is an extinct family of ginglymodian ray-finned fish that lived in what is now Africa, South America, and southern Europe during the Cretaceous period. They were close relatives of the modern gars of the family Lepisosteidae, with the two groups making up the superfamily Lepisosteoidea.

<i>Serenoichthys</i> Extinct genus of fishes

Serenoichthys is an extinct genus of small bichir from the Late Cretaceous (Cenomanian) of southeastern Morocco. The genus is monotypic, the type and only species being Serenoichthys kemkemensis. Only known at first from postcranial skeletons, complete specimens were later discovered.

This list of fossil fish research presented in 2024 is a list of new fossil taxa of jawless vertebrates, placoderms, cartilaginous fishes, bony fishes, and other fishes that were described during the year, as well as other significant discoveries and events related to paleoichthyology that occurred in 2024.

The Akrabou Formation is a Late Cretaceous -aged geological formation and Konservat-Lagerstätte in Morocco. It overlies the slightly older freshwater deposits of the Kem Kem Group, which it was once thought to be apart of. It was deposited over following the Kem Kem ecosystem's submergence by the Tethys Ocean during a marine transgression from the Cenomanian-Turonian boundary event, as part of a wider deposition of carbonate platforms across the region from the event.

References

  1. 1 2 3 4 5 6 Brito, Paulo M.; Dutheil, Didier B.; Gueriau, Pierre; Keith, Philippe; Carnevale, Giorgio; Britto, Marcelo; Meunier, François J.; Khalloufi, Bouziane; King, Andrew; de Amorim, Pedro F.; Costa, Wilson J. E. M. (2024). "A Saharan fossil and the dawn of Neotropical armoured catfishes in Gondwana". Gondwana Research . 132: 103–112. doi:10.1016/j.gr.2024.04.008.
  2. Cockerell, T. D. A. (1925-10-30). "A Fossil Fish of the Family Callichthyidae". Science . 62 (1609): 397–398. doi:10.1126/science.62.1609.397.c. ISSN   0036-8075.
  3. Lundberg, John G.; Sullivan, John P.; Rodiles-Hernández, Rocío; Hendrickson, Dean A. (2007-06-01). "Discovery of African roots for the Mesoamerican Chiapas catfish, Lacantunia enigmatica, requires an ancient intercontinental passage" (PDF). Proceedings of the Academy of Natural Sciences of Philadelphia . 156 (1): 39–53. doi:10.1635/0097-3157(2007)156[39:DOARFT]2.0.CO;2. ISSN   0097-3157.
  4. 1 2 3 Britz, Ralf; Pinion, Amanda K.; Kubicek, Kole M.; Conway, Kevin W. (2024). "Comment on "A Saharan fossil and the dawn of Neotropical armoured catfishes in Gondwana" by Brito et al". Gondwana Research . 133: 267–269. doi:10.1016/j.gr.2024.06.014.
  5. Brito, Paulo M.; Dutheil, Didier B.; Keith, Philippe; Carnevale, Giorgio; Meunier, François J.; Khalloufi, Bouziane; Gueriau, Pierre (2024). "A reply to a comment on Brito et al., 2024, A Saharan fossil and the dawn of the Neotropical armoured catfishes in Gondwana by Britz, Pinion, Kubicek and Conway". Gondwana Research. 133: 348–351. doi:10.1016/j.gr.2024.06.013.
  6. Filleul, Arnaud; Dutheil, Didier B. (2004-06-11). "A peculiar diplospondylous actinopterygian fish from the Cretaceous of Morocco". Journal of Vertebrate Paleontology . 24 (2): 290–298. doi:10.1671/3004. ISSN   0272-4634.
  7. Lemierre, Alfred; Blackburn, David C. (2022-07-15). "A new genus and species of frog from the Kem Kem (Morocco), the second neobatrachian from Cretaceous Africa". PeerJ . 10: e13699. doi: 10.7717/peerj.13699 . ISSN   2167-8359. PMC   9291016 . PMID   35860040.
  8. Ibrahim, N.; Sereno, P.C.; Varricchio, D.J.; Martill, D.M.; Dutheil, D.B.; Unwin, D.M.; Baidder, L.; Larsson, H.C.E.; Zouhri, S.; Kaoukaya, A. (2020). "Geology and paleontology of the Upper Cretaceous Kem Kem Group of eastern Morocco". ZooKeys (928): 1–216. doi: 10.3897/zookeys.928.47517 . PMC   7188693 . PMID   32362741.