The Chiapas catfish, ''Lacantunia enigmatica'', is an unusual species of

catfish Catfish (or catfishes; order Siluriformes or Nematognathi) 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 ...

(order Siluriformes) from the

Usumacinta River The Usumacinta River (; named after the howler monkey) is a river in southeastern Mexico and northwestern Guatemala. It is formed by the junction of the Pasión River, which arises in the Sierra de Santa Cruz (in Guatemala) and the Salinas ...

basin in the Mexican state of Chiapas and in Guatemala. It was

scientifically described A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have be ...

in 2005 and placed in its own

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Lacantuniidae. While discovery of an undescribed species of catfish is not uncommon, discovery of a new family of any

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...

group is a rare event. The Chiapas catfish mainly feeds on crabs,

prawn Prawn is a common name for small aquatic crustaceans with an exoskeleton and ten legs (which is a member of the order decapoda), some of which can be eaten. The term "prawn"Mortenson, Philip B (2010''This is not a weasel: a close look at nature' ...

s, small fish, and large, tough plant seeds. This catfish is commonly fished in its natural habitat, where it is known as ''madre de juil'', which means "mother of ''

Rhamdia ''Rhamdia'' is a genus of three-barbeled catfishes found in Mexico, Central and South America. These catfishes are nocturnal, opportunistic carnivores, found in a wide range of freshwater habitats. This genus includes a number of troglobitic me ...

''" (a common fish in the area).

Discovery

It first came to the attention of scientists in 1996, when Rócio Rodiles-Hernández, a Mexican ichthyologist conducting a biotic survey on the river, collected the first specimens from the Chiapas- Guatemala border. Unable to identify the species, Rodiles involved two American catfish specialists, Dean A. Hendrickson of the

University of Texas at Austin The University of Texas at Austin (UT Austin, UT, or Texas) is a public research university in Austin, Texas. It was founded in 1883 and is the oldest institution in the University of Texas System. With 40,916 undergraduate students, 11,07 ...

and John G. Lundberg of the

Academy of Natural Sciences The Academy of Natural Sciences of Drexel University, formerly the Academy of Natural Sciences of Philadelphia, is the oldest natural science research institution and museum in the Americas. It was founded in 1812, by many of the leading natura ...

of Philadelphia. A detailed comparative morphological study employing high-resolution
three-dimensional CT-scan imagery of the fish's anatomy
revealed a number of distinctive characteristics unique to this species and the absence of characters needed to place this fish in any existing catfish family. In a 2005 publication, these three ichthyologists, with Julian M. Humphries of the University of Texas, described this fish as a new species, genus and family of catfish.

Taxonomy

This fish is not related to any of the families found in its range (

Ariidae The Ariidae or ariid catfish are a family of catfish that mainly live in marine waters with many freshwater and brackish water species. They are found worldwide in tropical to warm temperate zones. The family includes about 143 species. Taxonomy ...

Ictaluridae The Ictaluridae, sometimes called ictalurids, are a family of catfish native to North America, where they are an important food source and sometimes fished for sport. The family includes about 51 species, some commonly known as bullheads, madt ...

, or

Heptapteridae The Heptapteridae, or three-barbeled catfishes, are a family of catfish that originate from the Americas. Most species are restricted to South America, but ''Imparfinis lineatus'', '' Nemuroglanis panamensis'' and ''Pimelodella chagresi'' are na ...

). It is most similar to Ictaluridae, but lacks some important characteristics to classify this fish into this family or the other two families. Initial study has placed this fish above

Diplomystidae 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. Taxonomy In traditional schemes, the fam ...

Cetopsidae The Cetopsidae are a small family of catfishes ( order Siluriformes), commonly called the whale catfishes. Taxonomy This family contains five genera divided into two subfamilies, Cetopsinae and Helogeneinae. Helogeneinae was previously a family ...

, and Hypsidoridae, but further classification is unknown. This family probably represents a basal group in which intermediates have disappeared. With recent molecular evidence, ''Lacantunia'' has been shown to be the sister group to

Claroteidae The Claroteidae are a family of catfish (order Siluriformes) found in Africa. This family was separated from Bagridae. However, the monophyly of the family is sometimes contested. The 12 genera contain 86 known species of claroteids in two subfa ...

, an

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

n catfish family. It probably diverged from the claroteids in the Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

between 75 and 90 mya.

Distribution and habitat

The generic name of the fish reflects its distribution in the

Lacantún River The Lacantún River is a river in Chiapas state of southern Mexico. It is a tributuary of the Usumacinta River. The Lacantún originates in the Chiapas Highlands, and runs southeastwards nearly to the Guatemalan border, where it turns northeastwar ...

drainage, flowing through the Montes Azules and Selva Lacandona Biosphere Reserves in Chiapas, Mexico into the

. After its initial discovery in the Lacantún, it was found to also inhabit other parts of the Usumacinta River basin, extending its range into northwestern Guatemala. With the description of the new family, four catfish families are now found in this region. These fish inhabit deep river channels and pools, often but not always with rocks and strong eddy currents. Few specimens were taken in stream mouths.

Physical characteristics

Key variations that differentiate this genus from all other families are the shape of the animal's

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

, jaw muscles, and gas bladder — which fish use to rise and sink in water. The gas bladder has paired diverticulae, while other catfish families either have no diverticulae or singular diverticulae. Some external characteristics that may help distinguish this fish include

nostril A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbi ...

s set far apart, the presences of nasal barbels, maxillary barbels placed above the lip distantly from the corner of the mouth, and a rounded caudal fin. This fish has four pairs of barbels. The maximum length of this species reaches SL. It is depressed (flattened) near the head and compressed (thin) near the tail. The head is blunt and rounded, and the mouth is usually not subterminal (down-turned). The adipose fin is large and thick. This fish has dorsal and pectoral fin spines.

References

External links

Chiapas catfish Tree of Life Web Project

Lacantunia enigmatica (Teleostei: Siluriformes) a new and phylogenetically puzzling freshwater fish from Mesoamerica
(an alternative link for the scientific paper describing this fish)
An unpublished first cladistic analysis of the Chiapas catfish (''Lacantunia enigmata'') among all catfishes and two anonymous reviews
{{Taxonbar, from=Q144246 Lacantuniidae Freshwater fish of Mexico Fish of Guatemala