Syndesus ambericus Woodruff, 2009

Woodruff, Robert E., 2009, A new fossil species of stag beetle from Dominican Republic amber, with Australasian connections (Coleoptera: Lucanidae), Insecta Mundi 2009 (98), pp. 1-10 : 2-7

Syndesus ambericus Woodruff , new species

Holotype. Amber fossil, Dominican Republic, probably Cordillera Septentrional. Deposited in the Brodzinsky-Lopez Peña Collection , USNM #502873 , Acc. # 371429, Woodruff # 5656, housed in the Department of Paleobiology, National Museum of Natural History, Washington, D.C. Enclosed in the same piece is a fly of the family Scatopsidae .

General Description. Specimen contained in amber, cut in cabochon form of elongate oval, convex on one side (referred to as dorsal) and relatively flat on the reverse (ventral). Dimensions: 37.5mm long, 20.5mm wide, 7.1mm thick (all maximum measurements); beetle fossil 13mm long (from mandible tip to abdomen tip), ca. 4mm high, width unmeasurable. Amber dark orange (darkened since first examined). Fractures presently obscuring many features, but Fig. 3 shows the specimen as it appeared in 1984. Body cylindrical, convex, elongate, with coarse punctures on pronotum and elytra. Habitus remarkably similar (compare Fig. 3 and 5 , lateral view) to the extant S. cornutus (Fabricius) .

Head broad, eyes large, prominent, nearly round. Antennal club large, with 7 lamellae ( Fig. 7 ); other antennomeres not visible. Head laterally with sharp projections in front of eyes (similar to Fig. 6 ). Maxillary palpi long, two-thirds mandible length, filiform, 3-segmented. Labial palpi 2-segmented, length half that of maxillary palpi. Mandibles prominent, symmetrical, horn-like, with 3 teeth ( Fig. 4 , 12), length two-thirds pronotal length.

Pronotum ( Fig. 3 , 10 ) convex, cylindrical, glabrous, coarsely punctate (most punctures deep and contiguous). Marginal line evident, appearing continuous laterally and posteriorly (no dorsal view). Medially with small projection, not carinate or sharply delineated, but clearly visible; concave below to head. Length two-thirds elytral length. Central furrow suggested in lateral view, but dorsal view obscured.

Elytra ( Fig. 3 , 8, 9 ) convex, cylindrical, glabrous; intervals (likely 10, difficult to count) prominently raised, intervening punctures coarse, deep, nearly contiguous. Fractures presently distorting and obscuring view. Pygidium not visible, but fine golden setae projecting at elytral margin. Margin appearing complete, terminating with smoothly rounded, gradual curve.

Legs similar to modern S. cornutus . Anterior tibiae dentate with 5 prominent teeth, becoming larger anteriorly, small teeth interspersed between each; spur broad, terminal.

Sex. Based on the sexual dimorphism in the Syndesinae , and shape of the mandibles, the specimen appears to be a male.

Comparisons. In most respects the fossil is so remarkably similar to the modern S. cornutus that there can be little doubt about the generic placement. Obvious specific differences are found in the mandibles, pronotal punctation, and pronotal projection (horn). The coarse, nearly contiguous pronotal punctures easily distiguish it from any known species.The mandibles of S. cornutus ( Fig.1, 5, 6 ) are more elongate and with only 2 teeth (points), whereas S. ambericus ( Fig. 4 , 8 , 12) mandibles are broader and have 3 teeth. The pronotal projection in S. cornutus (which is the origin of the specific name) is far more prominent and carinate ( Fig.1, 5, 6 ) than in S. ambericus ( Fig. 3 ). Few other character states are sufficiently visible in the fossil to distinguish it.

Etymology. The commercial amber fossil company formed by Jacob and Marianella Brodzinsky ( Woodruff 2004 b) was incorporated as “Amberica”, combining “Amber” and “America”. I have chosen to honor them for providing important fossils to the scientific community, by Latinizing their well-known company name.

Systematics. The family Lucanidae is not a large one by beetle standards. It has long been considered the ancestral stock within the Scarabaeoidea , and it contains many species with relict distributions. The latest checklist (Paulsen 2008), indicated 4 subfamilies, 109 genera, about 800 species, with 196 New World species in 32 genera, with only 24 Nearctic species in 8 genera. Paulsen (2005) stated that “ The classification of the family at the tribal level is currently superfluous...” There are no current keys to species in many genera (including Syndesus MacLeay ).

The genus Syndesus was created as the type of a new family by MacLeay (1819). In their treatment of the Lucanidae of the World, Didier and Séguy (1952, 1953) considered it as a subfamily ( Syndesinae ) with only 2 genera ( Syndesus and Psilodon Perty ). Within Syndesus , they recognized 5 species: 2 from Australia, 2 New Caledonia, and 1 erroneously from Africa ( Benesh 1955: 73); in Psilodon (with Hexaphyllum Grey as a synonym) were 3 species from South America. In Psilodon, Martinez and Reyes- Castillo (1985) and Boucher (1993) added new species from Brazil and Bolivia, respectively.

In his catalogue, Maes (1992) listed the subfamily Syndesinae to include Syndesus as the single genus (with Psilodon and Hexaphyllum as synonyms) of a separate tribe (Syndesini), along with Sinodendonini and Ceruchini. With this classification, the South American members ( Psilodon ) are combined with the Australasian ones, obscuring the disjunct distribution and morphological differences. Paulsen (2008) stated that “A meaningful classification of the Lucanidae at the tribal level cannot be created until all genera are properly diagnosed, and morphological and molecular phylogenetic analyses of the higher-level lucanid relationships are conducted.” That process was begun by Paulsen and Hawks (2008) when they described the new tribe Platyceroidini based on “...preliminary molecular analysis...(unpublished)” and morphological differences with Platycerini.

Ratcliffe (2002: 8) listed Syndesus and Psilodon as distinct. In his website checklist of 2005, Paulsen included the genus Psilodon as a synonym of Syndesus . However, in the most recent version (Paulsen 2008), the 2 genera are considered distinct. Several authors have weighed in on this classification ( Holloway 1960, 1968; Howden and Lawrence 1974; Kikuta 1986; Krajcik 2001; Mizunuma and Nagai 1994; Smith 2006), but there seems to be little agreement. As recent as 1993, a new species ( P. gilberti Boucher ) was described from Bolivia (Nor Yungas at 1500 meters). Unlike all other South American species of Psilodon , it has 7 lamellae in the antennal club, showing its relationship to the Australasian Syndesus . In fact, pronotal and mandible characters, illustrated in Boucher’s figures 6-7, show a remarkable similarity to S. cornutus from Australia. A thorough revision of both “genera” will be required to clarify their status. It is not my intent to evaluate classifications here, but to point out that the number of antennal lamellae (6 in Psilodon , 7 in Syndesus ) would appear to be a sufficient morphological character (along with their distributions) to separate these 2 “genera”. Although I have not examined all the species in either genus, Paulsen (2006) indicated that one species of Syndesus ( S. cancellatus Montrouzier ) has a 6-segmented club.

Provenance. There can be little doubt that this fossil is from the Dominican Republic. Brodzinsky never dealt in amber from elsewhere ( Woodruff 2004 b). Although he tried diligently to obtain specific locality data from the miners and suppliers, it was usually futile or unreliable. Because of color, inclusions, and vendor certainty, some pieces can be associated with specific mines. This specimen appears to have come from the Cordillera Septentrional (not the eastern, younger deposits). Brodzinsky said (personal communication) that it likely came from the famous Palo Quemado mine, located north of Santiago, near La Cumbre.

Age. There are no scientific techniques for dating amber itself. However, minimum ages can be obtained from associated microfossils in the sedimentary strata in which the amber is found. In the Dominican Republic, deposits were classified in the Altamira formation, once thought to be Eocene ( Hueber and Langenheim 1986). Lambert et al. (1985) and Poinar and Canatella (1987) reported on a frog, which was dated by a controversial technique (MRI) as Eocene. However, most mines in the Cordillera Septentrional are now considered to be marine sediments of Miocene age ( Grimaldi 1995; Iturralde-Vinent and McPhee 1996; Poinar 1992; Woodruff 1994). However, Dilcher et al. (1992) suggested that “...the amber clasts, from all physical characteristics, were already matured amber at the time of redeposition into marine basins. Therefore, the age of the amber is greater than Miocene and quite likely is as early as late Eocene”.

The age of Hispaniola continues to be controversial. Donnelly (1988) indicated that the Greater Antilles started emerging 105 million years ago, with a rapid increase in size about 80 million years ago. Ross and Scortese (1988) indicated that the Caribbean tectonic activity began in the Apian (118 million years ago), and Hispaniola may have begun to break from Cuba during the Oligocene (35 million years ago). Their exact size and position during subsequent geological periods is unknown, but most geologists agree that the Caribbean plate has moved many times, and individual islands occupied very different positions from today.

As I indicated earlier (Woodruff In Woodruff and Sanderson 2004), Hispaniola is composed of 2 separate tectonic plates, the southern one subducting under the northern main island. On this southern plate there is concrete evidence that land existed in the late Cretaceous (De León 1989) of Hispaniola. Fossil trees are found in this deposit in the southern island that are replaced by the volcanic mineral pectolite (var. Larimar; Woodruff 1986; Woodruff and Fritsch 1989). All amber deposits are found in the “north island”, but no amber has been discovered on this “south island” or on the Haitian side of the border.

Biogeographical significance. When such a disjunct presence of a species of Lucanidae is discovered as a fossil, and its relatives are geographically far removed, the initial question is “where did it originate?” West Indian biogeography has been a significant area of research in recent times, involving many geologists and biologists ( Woods 1989). However, many questions remain unresolved. The occurrence of various animal and plant species on each island have been documented both by dispersal and vicariance. Many fossil species (and entire groups) are no longer present.

The amber insect fossils offer a unique clue to these origins, and continue to supply our oldest evidence of past Caribbean history. Sanderson and Farr (1960) were the first to call attention to the rich amber fauna in the Dominican Republic, and the first Caribbean insect fossil was described a short time later ( Wille and Chandler 1964). A beautiful book, covering amber worldwide, was published by Grimaldi (1996). In the first catalogue of the Dominican Arthropod fossils (( Perez-Gelabert 1999), 508 species in 301 genera are recorded. In his latest magnificent catalogue of the Hispaniolan fauna ( Perez-Gelabert 2008), he recorded 6,833 extant and (unbelievably) 1,404 fossil species.

Because I was aware that no member of the family Lucanidae was known from the Caribbean, I was surprised to see this amber fossil from the Dominican Republic. When I later discovered its relationship to the Australasian fauna, I was even more incredulous. However, recent studies of Dominican amber fossils provide a growing list of similar distributions and relationships. Because they establish a pattern of ancient extinctions and biogeographical evidence, special examples are summarized below.

1. Leptomyrmex neotropicus Baroni-Urbani (1980) , and later ( Baroni-Urbani and Saunders 1982). The first fossil insect with Australian connections to be described from Dominican amber was this unusual ant. The genus is presently confined to Australia, New Guinea, and New Caledonia, leading Wilson (1985) to doubt the original placement of this amber fossil in the genus Leptomyrmex , although it was later confirmed ( Baroni-Urbani and Wilson 1987). Baroni-Urbani (1980) suggested that the disjunct distribution was the result of the genus having a “...former Tertiary cosmopolitanism or wide distribution...and a post Miocene contraction of the area.”

2. Valeseguya disjuncta Grimaldi (1991) . This woodgnat of the family Anisopodidae is a common amber fossil in the Dominican Republic. In fact, what was originally believed to be this species (subsequently identified as a species of Scatopsidae by D.A. Grimaldi 2009, in litt.) is present ( Fig. 3 , 11 ) in the amber piece with the Lucanid fossil described here. The type of the genus and the single other species is based on a unique extant male from Australia ( Colless 1990). Such a gap in distribution is not easily understood, except by one-time faunas being connected and subsequent extinctions. Grimaldi (1991: 13) emphasized that “There is no doubt about the close relationship between the extinct (Dominican) and living (Australian) species.”

3. Mastotermes electrodominicus ( Krishna and Grimaldi 1991) . This primitive, giant termite was described from Dominican amber, and it has 1 living relative; from Australia and New Guinea (another species has been described from Mexican amber). In Australia the living species thrives and is considered a serious pest species. This fossil was one of the first amber pieces to have DNA extracted ( DeSalle et al. 1992). Although retaining many roach-like features, the DNA studies suggested that these fossils were true termites and not “missing links” with the roaches ( Grimaldi 1996). In a recent paper ( Inward et al. 2007), comprehensive molecular studies show that termites are eusocial cockroaches; they relegate the Order Isoptera to a family ( Termitidae ) within the Order Blattodea .

4. Brachypsectra vivafosile (Woodruff 2002 [2004a]). When this unusual beetle was discovered, the family Brachypsectridae contained only 3 known species, with relict distributions ( India, Singapore, and South- western United States. Two larvae had been found in Dominican amber, but no adults. For this reason, the extant adult specimens were therefore considered “living fossils” (i.e., vivafosile ). An adult was found subsequently in Dominican amber and described as Brachypsectra moronei Branham (2006) . Recently a modern larva of the family was discovered in Australia ( Costa et al. 2006), but has not been named for lack of adults. It does establish additional evidence for the Australian-Dominican connection.

Extinction. Such distributions appear to be explained only by invoking theories of continental drift and plate tectonics. Grimaldi (1991) refers to this phenomenon as “geographical extinctions”. For the genus Syndesus (and many of the insects mentioned above) to be present in the Miocene Caribbean and modern Australasia, their ancestors must have once existed on the same land mass of the southern continent Gondwanaland, after the first division of the supercontinent Pangaea. These insects are extremely ancient relics of a much broader distribution!

Curiously, this ancient stag beetle (and any other species of Lucanidae present in the Miocene) became extinct in the Caribbean, while other scarab beetles seemed to proliferate, speciate, and evolve into island endemics. Presently, the scarab genus Phyllophaga contains 48 Hispaniolan species, all of which are confined to that island ( Woodruff and Sanderson 2004). Relationships to mainland faunas are obscure. Although the genus has hundreds of species in Central America, each Caribbean island appears to have mutually exclusive species.

Biology. Although there is no direct evidence for the behavior, biology, or habitats of this fossil, there is considerable general interest in postulating prehistoric environments ( Poinar 1999). This species probably lived in similar forests to extant species of the genus Syndesus . Most species of Lucanidae live in decaying wood, and often in larger tree trunks. Most are presently rare, localized, and difficult to locate; some (e.g., European stag beetle) are currently on endangered species lists. Their relict distributions include most climatic zones, except the Arctic and Antarctic. Virtually none has ever been considered of economic concern, although Lawrence (1981) reported an incident of Syndesus cornutus damaging a bridge support in Canberra, Australia.

Monteith (in litt. 2009) provided the following details of the biology of S. cornutus in Australia and Tasmania: It is one of the “really common species” in eastern Australia from Tasmania in the South to tropical Queensland in the north. It is found mostly in rainforests, but also occurs in Eucalyptus forests, especially at higher and damper sites. It breeds in wood with red rot fungi, mostly in large logs where big colonies build up and may persist for many years in the same log. Adults are often found in the galleries with the larvae. Adults come to lights “fairly regularly”.

Hueber and Langenhein (1986) pointed out that the tree which produced most Dominican amber was related to African ancestors, and it was later described as a new species by Poinar (1991). Dilcher et al. (1992) reported further on the leguminous trees from Dominican amber. The botanical inclusions are numerous, and many await taxonomic study. It appears that both insects and plants on the island of Hispaniola have some of their closest relatives currently living elsewhere!

Figures

Figure 1-6. Syndesus spp. 1, 2, 5, 6: Syndesus cornutus (Fab.). 1) Left lateral view of head and pronotum (note prominent mandibles and palpi). 2) Enlargement of eye and antenna (note 7 lamellae in club). 5) Habitus, lateral. 6) Habitus, dorsal. 3-4: Syndesus ambericus Woodruff, n. sp. 3) Amber fossil; habitus lateral in 1983. 4) Enlargement of right mandible (note 3 “teeth”).

Figure 7-11. Syndesus ambericus Woodruff, n. sp. 7) Antennal club (note 7 lamellae in club). 8) Lateral view, habitus; note fractures in 2009. 9) Enlargement of elytral punctures, right side. 10) Enlargement of pronotum; note dense, coarse punctures. 11) “Minute black scavenger fly” (Scatopsidae), located 5mm away from the Syndesus ambericus holotype. 12) Right lateral view of head and pronotum; note mandibles and palpi.