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Barbeled houndshark
The barbeled houndshark (''Leptocharias smithii'') is a species of ground shark and the only member of the family Leptochariidae. This demersal species is found in the coastal waters of the eastern Atlantic Ocean from Mauritania to Angola, at depths of . It favors muddy habitats, particularly around river mouths. The barbeled houndshark is characterized by a very slender body, nasal barbels, long furrows at the corners of the mouth, and sexually dimorphic teeth. Its maximum known length is .
Likely strong-swimming and opportunistic, the barbeled houndshark has been known to ingest bony fishes, invertebrates, fish eggs, and even inedible objects. It is viviparous with females bearing litters of 7 young; the developing embryos are sustained via a unique globular placental structure. The International Union for Conservation of Nature (IUCN) has assessed the barbeled houndshark as Near Threatened, as heavy fishing pressure occurs throughout its range and it is utilized for meat and leather.
==Taxonomy and phylogeny==
The genus ''Leptocharias'' was coined by South African physician and zoologist Andrew Smith, without any associated species, in an 1838 ''Magazine of Natural History'' article by Johannes Müller and Friedrich Henle. Müller and Henle added a species a year later in their ''Systematische Beschreibung der Plagiostomen'', but adopted the name ''Triaenodon smithii'' because they regarded ''Leptocharias'' as a junior synonym of ''Triaenodon''. Later authors recognized the validity of ''Leptocharias'', and shuffled it between the families Carcharhinidae and Triakidae before placing it in its own family. The type specimen is an adult male collected off Cabinda Province, Angola.
Because of its many unique characteristics, the evolutionary relationships of the barbeled houndshark are difficult to resolve. A morphological study by Compagno in 1988 was inconclusive on the relationship of ''Leptocharias'' to other carcharhiniform families. Similarly, a molecular phylogenetic study by López ''et al.'' in 2006 found that, though ''Leptocharias'' certainly belonged to a derived clade also containing the families Hemigaleidae, Triakidae, Carcharhinidae and Sphyrnidae, its position within that group changed depending on the DNA sequence and type of analysis used. Fossilized teeth belonging to an extinct relative, ''L. cretaceus'', have been recovered from Late Cretaceous (Santonian and Campanian ages, 86–72 Ma) deposits in Britain.
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