Tyrannasorus rex Ratcliffe and Ocampo

Ratcliffe, Brett C. & Ocampo, Federico C., 2001, Tyrannasorus rex Ratcliffe And Ocampo, A New Genus And Species Of Miocene Hybosorid In Amber From The Dominican Republic (Coleoptera: Scarabaeoidea: Hybosoridae), The Coleopterists Bulletin 55 (3), pp. 351-355 : 353-354

Tyrannasorus rex Ratcliffe and Ocampo , new species

Figs. 1– 9

Type Material. Holotype (probably female) from the Dominican Republic, specimen number AMNH DR­10–702 , embedded in amber, age Miocene . Holotype deposited in the Amber Fossil Collection, Dept. of Entomology, American Museum of Natural History, New York.

Description. Holotype. Length 5.8 mm; greatest width 2.7 mm. Color reddish brown. Head: Frons with surface irregularly punctate, punctures moderate in size and density. Eye canthus elongate, subrectangular, apex truncate. Frontoclypeal suture not visible. Clypeus with surface similar to that of frons, anterior margin truncate, lateral margin arcuate and narrowly reflexed. Mandibles large, external edge broadly rounded; dorsal surface smooth, slightly concave, apex with well­developed, dorsal, subapical tooth ( Figs. 3 , 5 ). Maxilla and galea with dense, slender setae; maxillary palpus with 4 segments, first segment short, second longer than first or third, fourth longer than second and third combined. Labium with numerous long setae. Pronotum: Surface weakly convex, irregularly punctate; punctures moderate in size and density. Scutellum: Shape subtriangular, apex slightly rounded. Elytra: Surface smooth, with sparse, minute punctures that do not delimit striae or intervals. Humeral umbone weakly elevated. Legs: Protibia ( Figs. 4 , 7 ) on external margin with 3 long, acute teeth and with 7 denticles behind basal tooth and 2 denticles between median and basal teeth; apical spur reaches apex of second tarsal segment. Protarsus with basal segment long, segments 2–4 subequal in length and shorter than first, each with slender distal setae; fifth segment slightly longer than any of segments 2–4. Meso­ and metatarsi with segments 1 and 5 longer than any others, segments 2–4 subequal in length; segments 1–5 each with pair of setae at apex.

Remarks. We surmise that the holotype is a female based on the presence of character states for the foretibia and tarsal claws that are the same for females in the genus Apalonychus , a genus of hybosorid that also occurs in the West Indies. Certain characters of the body (especially ventrally) cannot be seen because of the dark nature of the amber.

The tree that produced the resin that trapped this specimen is Hymenaea protera Poinar (Leguminosae, Caesalpinioideae). The amber in which it is embedded has been dated as Miocene in age ( Grimaldi 1995). Iturralde­Vinent and MacPhee (1996) indicated that all the main amberiferous deposits in the Dominican Republic (including those with biological inclusions) were formed in a single sedimentary basin during the late Early Miocene through early Middle Miocene (15–20 million years ago). Previous dating of Dominican amber as Oligocene or especially Eocene ( Lambert et al. 1985) is probably erroneous (Grimaldi, pers. comm., 2000; Iturralde­Vinent and MacPhee 1996). A specific collecting locality for the specimen is not possible because virtually all amber material in the Domincan Republic is purchased from miners by dealers who then sell it to researchers and collectors. The amber piece probably came from the northern mountain range north of Santiago de los Caballeros in the Dominican Republic where most of the mines are located. The amberbearing unit comprises the upper 300 m of the La Toca Formation and consists of sandstone interspersed with a conglomerate of pebbles, organic matter, and thin coal lamellae ( Iturralde­Vinent and MacPhee 1996). The amber occurs in the lignite­rich sandstone beds or in lignite seams (Eberle et. al 1980; Grimaldi 1996).

Etymology. From the Latin rex , meaning ‘‘king’’... a play of words on another famous, and much larger, species of extinct animal that has a similarsounding generic name.

Figures

Figs. 1–4. Holotype of T. rex embedded in amber. 1) Dorsal view; 2) oblique ventral view; 3) dorsal view of head and pronotum; note especially antenna, clypeus, and mandibles; eyes are not dorsally visible; 4) anterior view of head and proleg.

Figs. 5–9. Line drawings of T. rex. 5) Dorsal view of head and pronotum; 6) dorsal view of left antenna; 7) dorsal view of left proleg; 8) ventral view of left middle leg; 9) ventral view of left posterior leg.