Forelius chenpauch Varela-Hernández & Riquelme & Guerrero 2023, sp. nov.
Creators: name: Varela-Hernández, Fernando
name: Riquelme, Francisco
name: Guerrero, Roberto J.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Formicidae
Forelius
Forelius chenpauch

description: Forelius chenpauch sp. nov. Varela-Hernández, Guerrero and Riquelme
(Figures 1-2)
zoobank.org/ 795FBFFB-5934-4259-899E-E60A69DA1319
Etymology. The specific epithet chenpauch means “from the amber cave” in the Tzotzil language, a name given by the local people of the Simojovel to the amber mines or pits.
Type material. Holotype CPAL. 464 Worker, amber inclusion, complete specimen. It is deposited in the Colección de Paleontología, UAEM, Morelos, Mexico (Figure 1A)
Locality. Mexico, Chiapas, Simojovel, Montecristo mine: 17° 7' 45.99" N, 92°41'43" W.
Distribution. It is only known from the Miocene strata of Simojovel, Chiapas, southern Mexico.
Horizon. The Mazantic and Balumtum strata, Early Miocene (ca. 23 Ma).
Diagnosis. Antennal scape reaching the posterior margin of the head; pronotum with six erect hairs; mesonotum with four erect hairs; propodeum with four erect thin hairs; front and dorsum of head, dorsum of pronotum, dorsum of mesonotum, and propodeum covered with fine longitudinal striae.
Worker description
Measurements (mm). TL: 2.0; HL: 0.6; HW: 0.6; EL: 0.1; EW: 0.1; IOD: 0.4; SL: 0.5; PSL: 0.05; PSW: 0.05; MsL: 0.8; CI: 100; OI: 100; SI: 83.33.
Head. As long as broad; vertex of head weakly concave; antennal scapes reaching the posterior margin of the head; mandible with a basal and masticator margin differentiated, with six observable teeth in the latter (Figure 2B); clypeus with two slender, erect setae projecting onto the mandibles at the middle part, about the level of the antennal insertions; two other shorter setae on each side of the erect setae described previously: one at the lateral edge of the mandible and another between the latter and the one at the middle of the mandible; the dorsal face of mandibles covered with decumbent pilosity; dorsum of head finely striated (Figures 1B, 2A, 2B).
Mesosoma. Dorsal profile discontinuous. In dorsal view, well-impressed promesonotal suture; weak mesonotal groove in lateral view; pronotum with six thin, erect hairs, four located anteriorly, longer than the other two located posteriorly, two at the anteriormost humeral and the other two at the middle; dorsal surface of pronotum and mesonotum with weak transversal striae; dorsal and posterior face of propodeum rounded, with no apparent angle that differentiates the two faces; one pair of thin, erect hairs located dorsolaterally on the propodeum dorsal face and another pair posterolaterally on the propodeum posterior face; propodeal spiracle small and rounded (Figure 2A, 2B). Legs without pilosity.
Petiole. Scale present, inclined anteriorly, with a pair of erect setae, barely visible.
Gaster. First and second tergite with a row of short, thin, erect setae running along the apical fringe of tergites, sternites lost; gaster concolorous yellow with mesosoma.
Remarks. The worker (Holotype CPAL.464) studied here is classified in the genus Forelius since it presents the diagnostic characters of the genus, that is, the anterior clypeal margin with two long curved setae is observed in the specimen, which, although in the specimen the mandible is open, these clypeal hairs project reaching the external margin of the mandible. The configuration of the mandible and the dentition pattern on the masticatory margin agree with that of Forelius according to Shattuck (1992), that is, mandible with a smooth basal and masticatory margin differentiated, the latter armed with 6-7 teeth. The petiolar scale is reduced and strongly inclined anteriorly as well, however, in the specimen it appears relatively straight (Figures 1-2), but it is due to the position within the amber piece. The latter also makes it difficult to observe the first gastral segment projecting anteriorly and concealing petiole in dorsal view; however, an inclined view of the piece allowed us to observe a shallow depression on the anterior face of the first gastral tergite. Forelius chenpauch sp. nov. is a species with a rounded spiracle but differs from other Forelius species with this same condition by the characters listed below (Table 1).
Forelius chenpauch sp. nov. could be confused with extant dolichoderine ants of the genus Liometopum Mayr, 1861 and the genus Tapinoma Foerster, 1850, which can currently be found in Mexico. However, Forelius chenpauch sp. nov. is distinguished by having a mandible with a basal margin distinct from the masticatory margin (Figures 1A, 1B, 2B), whereas Liometopum and Tapinoma have an undifferentiated basal margin. In addition, Forelius chenpauch sp. nov. has a petiole scale anteriorly inclined (Figures 1A, 2A, 2B). In contrast, Liometopum has a vertical petiolar scale, that is, never anteriorly inclined; and in the currently known Neotropical species of Tapinoma the petiolar scale is strongly reduced, in most hidden by the first gastral segment (Guerrero unpublished data).
On the other hand, the genus Forelius and the genus Azteca Forel, 1878 have been recorded in Mexican and Dominican amber (Duran-Ruiz et al., 2013; Barden, 2017). However, the fossil record of Forelius is uncommon in both deposits, whereas Azteca is more frequent. Forelius is composed of hyperactive thermophilic ground-nesting ants (Ward, 2005) that are adapted to living in arid to semi-arid areas (Shattuck, 1992; Cuezzo, 2000) whilst Azteca encompasses ants that nest mainly in trees (Longino, 2007). Notably, the species Azteca alpha Wilson, 1985 constitutes 30 to 50% of the total number of ants found in Dominican amber (Barden, 2017). The highest frequency of Azteca records is consistent with an arboreal environment. The sedimentary data in Mexican amber deposits suggests a lowland fluvial environment close to the coastal plain (Allison, 1967; Frost and Langenheim, 1974; Graham, 1999; Langenheim, 2003; Riquelme et al., 2014a, 2015). Accordingly, the leguminous trees of Hymenaea (the botanical source of Mexican amber) were part of a tropical forest resembling modern mangroves (Langenheim, 2003) where a warmer (+1.99 °C) and drier (− 337.7 mm) tropical climate have been estimated than the current average records (Hernández-Hernández et al., 2020). Although forested areas may have predominated, the Miocene tropical forest in southern Mexico possibly presented minor arid to semi-arid zones that the Forelius could exploit to locate the colonies.
description: Published as part of Varela-Hernández, Fernando, Riquelme, Francisco & Guerrero, Roberto J., 2023, A Miocene ant species of the genus Forelius Emery, 1888 (Hymenoptera: Formicidae: Dolichoderinae) from Mexico, pp. 1-9 in Palaeontologia Electronica (a 36) (a 36) 26 (3) on pages 3-6, DOI: 10.26879/1294, http://zenodo.org/record/10962179