Tyrannasorus 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 : 351-354

Tyrannasorus Ratcliffe and Ocampo , new genus

Type Species. Tyrannasorus rex Ratcliffe and Ocampo.

Description. Body form ( Fig. 1 ) convex, subglobose. Color reddish brown. Head: Frons irregularly punctate, lateral margins narrowly reflexed. Clypeus with anterior margin truncate. Labrum protruding beyond clypeus, weakly trapezoidal, wider at apex, with series of setae either side of middle. Antennae ( Figs. 3 , 6 ) with 9 segments; basal segment apically expanded, with long erect setae on anterior side, second segment broader than long, third segment about twice as long as wide, fourth as long as wide, fifth and sixth wider than long, fifth with 2 setae; club 3­segmented with basal segment weakly hollowed to receive second and some of third segment; all segments tomentose. Pronotum: Surface weakly convex. Anterior margin sinuate; anterior angles strongly produced, subacutely rounded ( Fig. 3 ); lateral margins rounded, widest just behind middle; posterior angles broadly rounded; posterior margin sinuate, produced backward at middle; anterior and lateral margins with marginal bead. Scutellum: Surface smooth. Elytra: Shape convex, subglobose. Lateral margins rounded, widest at middle, and with marginal bead. Legs: Claws on all legs simple. Meso­ and metatibiae ( Figs. 8–9 ) with transverse ridge near middle of external surface, ridge with erect setae on margin; apex with 2 spurs, external spur much longer than first segment of respective tarsus, median spur shorter than first tarsal segment; apex of tibiae truncate, dilated, with large, rounded, flattened lobe on external edge, lobe with crown of setae.

Remarks. The genus Tyrannasorus is unique among other hybosorids from the West Indies because its has 9­segmented antennae whereas all the other genera have 10­segmented antennae. The genus Tyrannasorus is similar to the genera Coilodes and Apalonychus in the following characters: body form convex, subglobose; color reddish brown; apex of tibiae truncate, dilated, and with a large, rounded, flattened lobe on its external edge, lobe with terminal crown of setae. Coilodes species are different from Tyrannasorus species because they have a cup­shaped antennal club (only weakly concave in Tyrannasorus ), a labrum wider at its base, and the anterior margin of pronotum not sinuate. Apalonychus species are different from Tyrannasorus species because they have the club of the antenna much more elongated, a labrum wider at its base, the anterior margin of pronotum not sinuate, and eyes subglobose and clearly visible in dorsal view (eyes not clearly visible in dorsal view for Tyrannasorus ).

Etymology. The loosely formed stem of this name, tyranna, is from the Latin tyrannus, indicating ‘‘master’’ or ‘‘tyrannical.’’ The suffix sorus is Latin meaning ‘‘hump’’ or ‘‘pile’’, and it is also the suffix for the family name of Hybosoridae and its type genus, Hybosorus . Hence, we have the tyrannical hump, suggesting the possible state of ‘‘mind’’ (ganglion?) of this small, humped beetle getting hopelessly stuck in a blob of sticky Hymenaea sap. The genus is masculine in gender.

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. Ho­

lotype 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.