Lonchidionoides

Lonchidionoides Temporal range: Barremian–Cenomanian PreꞒ Ꞓ O S D C P T J K Pg N
Teeth of L. trifurcatum from the Tiout Formation, Algeria
Lonchidionoides sp. teeth from the Fazenda Tereza locality.
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Order:	†Hybodontiformes
Family:	†Lonchidiidae
Genus:	†Lonchidionoides Vullo et al., 2026
Type species
†Lonchidionoides trifurcatum Vullo et al., 2026

Lonchidionoides is an extinct genus of lonchidiid hybodont, known from the Barremian-Aptian of Brazil and the latest Albian-early Cenomanian of Algeria. The type species is L. trifurcatum from the uppermost Albian–lower Cenomanian Tiout Formation of Algeria. Teeth of this genus are also known from the Barremian–Aptian 'Fazenda Tereza' locality of the Quiricó Formation of Brazil, which have been left in open nomenclature as L. sp. pending new material.^[1]

Discovery and naming

Localities where Lonchidionoides teeth were found

The teeth of L. trifurcatum were discovered from the 'Garet El Hemmam' locality in the Laghouat Province of northern Algeria, which is a part of the Tiout Formation and consist of 5 teeth.

The teeth from Brazil were previously described as ?Lonchidiidae in 2021.^[2] The available Brazilian Lonchidionoides material are essentially identical in morphology and size to L. trifurcatum, they remain in open nomenclature as L. sp., awaiting further specimens that would allow more precise taxonomy.The specimans consist of 9 teeth.^[1]

In 2026 Vullo et al., 2026 described Lonchidionoides as a new genus of Lonchidiid hybodonts and described 2 species one unnamed species from the Early Cretaceous of Brazil and L. trifurcatum from the Early-Late Cretaceous of Algeria. The etymology of Lonchidionodes derives from its similarity to the teeth of the namesake of its family Lonchidion itself. While the etymology of the species name of L. trifurcatum refers to the trident shape of the anterior teeth. ^[1]

L.trifructatum is diagnosed by the following features : marked disjunct monognathic heterodonty; gracile, trident-shaped anterior teeth and low-cusped, more massively built posterior teeth, lateral teeth showing an intermediate morphology with no labial protuberance, a narrow and rod-like shaped crown bas and an enameloid smooth and a tooth crown devoid of ornamentation.^[1]

Description

A tentative reconstruction of the dentition of the lower jaw of L.trifurcatum

The teeth are minute, most of the specimens measuring less than 1 mm in width. All the specimens consist of well-preserved crowns with no preserved roots. The basal face of the crown is depressed. Three main dental morphotypes can be distinguished. With morphotype 1 corresponding to anterior teeth, morphotype 2 corresponding to lateral teeth and morphotype 3 corresponding to posterior teeth (with the first prosterior tooth being adapted for crushing).^[1]

Paleoenvironment

Lonchidionoides trifurcatum were discovered froAll of the Hcalsin Algr exposes the Tiout Formation. Thi assigned to the upparious other es, such be like Bawitius, sarcoptergians like mawsoniids and Neoceratodus africanus, turtles, crocodyliforms, and the famous theropod dinosaurs Spinosaurus aegyptiacus and Carcharodontosaurus saharicus.

Vullo et al. also assigned fossil teeth from Brazil, previously described as ?Lonchidiidae,^[2] to Lonchidionoides. These specimens were discovered from the Quiricó Formation exposed at the 'Fazenda Tereza' locality in the Sanfranciscana Basin of Brazil, which also preserves other hybodontiforms, amiids, Mawsonia gigas, and the paramacellodid lizard Neokotus sanfranciscanus. Although this formation is typically assigned to the Barremian-Aptian, there have been arguments that the 'Fazenda Tereza' locality may represent older strata.

References

1. Vullo, Romain; Fragoso, Léo Galvão Carnier; Bittencourt, Jonathas S.; Pérez-García, Adán; Bouchemla, Imad; Benyoucef, Madani (2026). "A new genus of lonchidiid hybodontiform sharks from the Cretaceous of North Africa and South America". Geological Magazine. 163. doi:10.1017/S0016756825100484. ISSN 0016-7568.
2. Fragoso, Léo Galvão Carnier; Bittencourt, Jonathas S.; Mateus, Ana Luisa D; Cozzuol, Mario Alberto; Richter, Martha (2021). "Shark (Chondrichthyes) microremains from the Lower Cretaceous Quiricó Formation, Sanfranciscana Basin, Southeast Brazil". Historical Biology. 33 (8): 1308–1316. doi:10.1080/08912963.2019.1692830.