The genus Trigonognathus Mochizuki and Ohe, 1990, is a monospecific taxon of `lantern sharks¿ (i.e., family Etmopteridae), a group of small-sized bioluminescent deep-sea chondrichthyans, ranging in mature male specimens between 42¿47 cm total length, and at least 52 cm for females (Ebert et al., 2021). This shark inhabits the upper continental slopes as well as the uppermost slope of seamounts, often at the bottom, at depths ranging between 250¿1000 m, but has been caught at 150 m and 270 m in deep open waters (Mochizuki and Ohe, 1990; Compagno et al., 2005; Ebert et al., 2021). Only two species have been described thus far, the extant species Trigonognathus kabeyai Mochizuki and Ohe, 1990, and the extinct ¿Trigonognathus virginiae from the middle Eocene of France (Cappetta and Adnet, 2001). Trigonognathus kabeyai exhibits a combination of morphological characteristics that are unique among Squaliformes, like a highly protrudable jaw articulation (Shirai and Okamura, 1992; Straube et al., 2010), and a lack of dignathic heterodonty. Additionally, the tearing-type dentition, and strong monognathic heterodonty with hypertrophied anterior teeth, differentiate it from the genus Squalus and Cirrigaleus (with cutting-type dentition), and Centroscyllium and Aculeola (with no monognathic heterodonty and clutching-type dentition) (Cappetta and Adnet, 2001). The geographic distribution of T. kabeyai is restricted to the Pacific Ocean, in the Wakayama and Tokushima coasts of Japan (Mochizuki and Ohe, 1990; Shirai and Okamura, 1992; Ebert et al., 2021), Taiwan (Ebert et al., 2013), and in the north-west of Hawaii (Wetherbee and Kajiura, 2000). However, the fossil record of the genus Trigonognathus indicates a broader geographic distribution in the past (Aguilera and Rodriguez de Aguilera, 2001; Cappetta and Adnet, 2001; Carrillo-Briceño et al., 2015). These findings include ¿T. virginiae from the middle Eocene of Landes (eastern Atlantic), southwestern France (Cappetta and Adnet, 2001), and two isolated teeth assigned to Trigonognathus sp. and Trigonognathus aff. kabeyai from the Upper Miocene of Panama (Carrillo-Briceño et al., 2015) and the Upper Miocene¿Lower Pliocene of Venezuela (Caribbean Sea) (Aguilera and Rodriguez de Aguilera, 2001), respectively. Given the apparent rarity of this elusive taxon, any new finding, especially in the fossil record, is of note and increases our knowledge of this genus. Herein we describe a Middle Miocene locality with the first known record of Trigonognathus in the Mediterranean realm (south-eastern Spain), which offers new insight into the paleoenvironmental and paleobiogeographic history of this shark. In addition, with the objective of providing new information about possible diagnostic characteristics of the genus, the first description of its internal tooth histology is provided.