Cananeuretus, ENGEL & GRIMALDI, 2005

ENGEL, MICHAEL S. & GRIMALDI, DAVID A., 2005, Primitive New Ants in Cretaceous Amber from Myanmar, New Jersey, and Canada (Hymenoptera: Formicidae), American Museum Novitates 3485, pp. 1-24 : 17-19

† Cananeuretus , new genus

TYPE SPECIES: † Cananeuretus occidentalis , new species.

DIAGNOSIS: Compound eyes present, small; ocelli absent. Antennal sockets slightly inclined; scape elongate. Mandible of primitive construction, with four distinct teeth (fig. 10), basalmost tooth largest. Preoccipital carina absent; ocelli absent. Alitrunk elongate, slen­ der; pronotal neck elongate. Meso­ and metatibia with a single spur; pretarsal claws simple. Propodeal lobes, denticles, and spines absent; petiole one­segmented, anterior peduncle elongate, with distinct tubular, postnodal section (more elongate than in Aneuretus ) articulating high on anterior surface of second metasomal segment, petiolar tergum and sternum fused; nodus not very high. Metasoma excluding petiole short and globular; without U­shaped emargination on anterior margin of second metasomal segment; sting present and well developed. Known from the worker caste only.

ETYMOLOGY: The new genus­group name is a combination of Canada, the country from which this amber originates, and Aneuretus , type genus of the Aneuretinae . The name is masculine.

COMMENTS: † Cananeuretus might at first be confused for † Eotapinoma , a dolichoderine described from Canadian amber ( Dlussky, 1999). † Cananeuretus differs notably from † Eotapinoma in the presence of a welldeveloped sting (apparently vestigial in † Eotapinoma , like all dolichoderines), the more elongate petiole with a distinct nodus (shorter petiole, which does not have an elongate peduncle and without developed nodus in † Eotapinoma ), and the reduced compound eyes (large in † Eotapinoma ).

This new genus is tentatively placed in Aneuretinae , although the group shows mostly what are presumed plesiomorphies for the subfamily. The presence of a strong, welldeveloped sting and absence of an acidopore excludes placement in Dolichoderinae or Formicinae. However, the genus is best placed among the formicomorph subfamilies (sensu Bolton, 2003) where it most closely approximates the Aneuretinae . As more material is recovered of these ants and a cladistic framework for fossil aneuretines achieved, it is possible that † Cananeuretus and others may prove to be stem­group Aneuretinae or even represent stem groups to Aneuretinae 1 Dolichoderinae .

Today the subfamily Aneuretinae consists of a single species occurring in Sri Lanka. During the Tertiary aneuretines were distributed widely in the Northern Hemisphere as evidenced by their occurrence in Baltic amber ( Wheeler, 1914) and Florissant, Colorado ( Carpenter, 1930). The mid­Cretaceous genus † Burmomyrma , in amber from Myanmar, has been tentatively placed in the Aneuretinae ( Dlussky, 1996; Bolton, 2003) and, until now, represented the sole Mesozoic record for the subfamily. It is increasingly apparent that aneuretines were widely distributed during the Mesozoic and early Tertiary, and that Aneuretus is a notable relict in Sri Lanka today. The significant extinction of northern aneuretines was perhaps a result of the infamous Eocene­Oligocene climatic shift, a cooling event that dramatically altered the evolutionary history and biogeography of numerous insect lineages that are today austral relicts ( Grimaldi and Engel, 2005).

† Cananeuretus occidentalis , new species

Figures 2 , 10–11

DIAGNOSIS: As for the genus (vide supra). DESCRIPTION: Body with sparsely scattered,

fine setae; integument finely imbricate. Head. Length ca. 0.52 mm; narrowed slightly toward apex; vertex gently rounded. Mandibles with short, pointed teeth, basalmost apical tooth largest. Eyes present, relatively small and low on head (difficult to observe). Scape fairly long (0.46 mm), narrowed slightly at base for articulation with bulb (fig. 10); pedicel 0.653 length of scape. Mesosoma. Elongate, not deep, length ca. 3.10 mm; pronotum forming a distinct neck anteriorly. Legs slender and long; trochantellus present (fig. 11). Inner surfaces of protibia and probasitarsus with row of short, fine setae forming weakly defined brushes (fig. 10); tarsomeres beyond basitarsus triangular, laterally with short, distinct, stiff setae; pretarsal claws simple. Mesotibia and metatibia with a single spur; metatibial spur distinctly and minutely setose (fig. 10). Propodeum without lobes or spines, broadly rounded and gently sloping to articulation with petiole. Metasoma. Petiole with elongate peduncle, distinct nodus, and relatively long posterior, tubular section, articulating high on second metasomal segment; petiolar tergum and sternum fused; metasoma without constriction between second and third segments (i.e., gastral segments 1 and 2); metasoma overall quite globular. Sting well developed, extrud­ ed.

HOLOTYPE: TMP 8.89 .7, labeled, ‘‘ Grassy Lake, Alberta, Campanian, Foremost Formation , Formicidae’ ’ (figs. 2, 10). Worker in amber that is embedded in a thin block of epoxy and slide mounted.

ADDITIONAL MATERIAL: TMP 91.149.3, labeled, ‘‘ Hymenoptera, Grassy Lake , Alberta, Campanian, Foremost Formation, Formicidae’’ (fig. 11). Worker in amber that is embedded in a thin block of epoxy and slide mounted. The specimen is partial and owing to some minor differences in the shape of the petiole, we have considered it best to only tentatively assign it to this species.

ETYMOLOGY: The specific epithet is the term occidentalis , meaning ‘‘of the west’’, and is a reference to this being the first aneuretine or aneuretine­like ant from the Mesozoic of the Western Hemisphere.

Figures

Figs. 1–3. Three Cretaceous amber ants. 1. †Myanmyrma gracilis, new genus and species (AMNH Bu­014) in Burmese amber. 2. †Cananeuretus occidentalis, new genus and species (TMP 8.89.7) in Canadian amber. 3. †Sphecomyrmodes orientalis, new genus and species (AMNH Bu­351) in Burmese amber.

Fig. 10. Holotype worker of †Cananeuretus occidentalis, new genus and species (TMP 8.89.7).

Fig. 11. Partial worker of †Cananeuretus occidentalis? (TMP 91.149.3).