Pheidole praehistorica

AntWiki: The Ants --- Online
†Pheidole praehistorica
Temporal range: middle Miocene
↓
Mexican amber, Chiapas, Mexico
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Pheidole
Species: †P. praehistorica
Binomial name
†Pheidole praehistorica
Varela-Hernández & Riquelme, 2024

Pheidole praehistorica is known from the late Oligocene and early Miocene amber-bearing beds of Mexico. The type material comprises five amber inclusions from the Simojovel site in Chiapas. It shows close morphological and phylogenetic affinities with Pheidole primigenia and Pheidole tethepa from Dominican amber, which may suggest that the shared spinescence character in Pheidole has a probable New World ancestry. The record of P. praehistorica in the Oligo–Miocene strata of southernmost North America provides further evidence for the ancient distribution of spiny ants of the genus Pheidole in the New World.

Photo Gallery

  • Varela-Hernández & Riquelme (2024), Fig. 1. Pheidole praehistorica. A–C. Holotype (CPAL.464). A. Profile view. B. Frontal view. C. Closer lateral view of the head and mesosoma. D. Paratype (CPAL.465), latero-frontal view of the head. E. Paratype (CPAL.468), profile view. Abbreviations: acl = antennal club; an = antenna; cly = clypeus; ey = eyes; fl = foreleg; ga = gaster; ha = hairs on clypeus; hd = head; hl = hind leg; mn = mandible; nck = neck; p = petiole; pn = pronotum; pns = pronotal spine; pp = postpetiole; pps = propodeal spine; sc = scape.
  • Varela-Hernández & Riquelme (2024), Fig. 2. Pheidole praehistorica, holotype (CPAL.464), schematic drawing. A. Profile view. B. Frontal view.

Identification

Pheidole praehistorica differs significantly from the other two Dominican fossil spiny species as follows: Pheidole primigenia has an average size of 2.88–3.56 mm, while P. praehistorica is smaller, with an average total length of 2.3 mm. It also differs by longer pronotal spines in P. primigenia and smaller ones in P. praehistorica. Pheidole praehistorica has a deeper mesonotal groove than P. primigenia; propodeal spines are curved downwards in P. primigenia but straight in P. praehistorica; P. primigenia differs markedly by the shape of the anterior edge of the clypeus, which is “slightly prominent in the middle and straight” (Baroni-Urbani 1995), while it is formed by a median projection with a minute denticle in the middle and a lateral denticle on each side of the median projection in P. praehistorica (Fig. 1A–E).

Pheidole tethepa is another fossil species from Dominican amber with pronotal spines similar to those of P. primigenia and P. praehistorica. However, P. tethepa has a pair of gular spines not found in P. primigenia or P. praehistorica. In contrast, P. primigenia and P. praehistorica have a well-formed head collar not found in P. tethepa. In addition, P. tethepa differs markedly from P. praehistorica in the shape of the middle of the anterior edge of the clypeus which is convex in P. tethepa, but in P. praehistorica it is formed by a median projection with a tiny denticle at its middle.

Distribution

This taxon was described from Mexican amber, Chiapas, Mexico (Middle Miocene).

Locality and horizon: Mexico, Chiapas, Simojovel, Montrecristo mine: 17°09′11″ N, 92°46′08″ W. Upper strata of the Simojovel Formation at the late Oligocene and early Miocene boundary (Riquelme et al. 2024).

Castes

Phylogeny

  • Varela-Hernández & Riquelme (2024), Fig. 3. The phylogenetic status of Pheidole praehistorica among fossil and extant congeners inferred from the list of characters (Supp. file 1: Table S1) and the data matrix (Supp. file 1: Table S2), shows the twenty-eight morphological characters to construct the most parsimonious tree. The numbers above the white and black dots represent morphological characters, and the numbers below represent the character encoding. Black dots represent synapomorphies, and white dots represent homoplasies. † represents fossil species from Dominican and Mexican amber. Consistency index = 0.52; retention index = 0.65.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • †praehistorica. †Pheidole praehistorica Varela-Hernández & Riquelme, 2024: 89, figs. 1-3 (w.) MEXICO (Chiapas, Oligo-Miocene Mexican amber).

Type Material

  • Holotype: MEXICO • Chiapas, Simojovel, Montrecristo mine; 17°09′11″ N, 92°46′08″ W; CPAL-UAEM, CPAL.464 (Fig. 1A–C).
  • Paratypes: MEXICO • 4 specs; same data as for holot0ype; CPAL-UAEM, CPAL.465 to CPAL.468 (Fig. 1D–E).

The paratypes are fossil inclusions, complete articulated specimens except CPAL.468, which is disarticulated medially (Fig. 1E). All specimens are embedded in a single piece of amber, surrounded by plant remains and soil. They are housed in the Colección de Paleontología (CPAL-UAEM), Morelos, Mexico.

Description

References

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