Ceafornotensis, Woolley, Christopher, 2016

Woolley, Christopher, 2016, The first scarabaeid beetle (Coleoptera, Scarabaeidae, Melolonthinae) described from the Mesozoic (Late-Cretaceous) of Africa, African Invertebrates 57 (1), pp. 53-66 : 54-55

Taxon classification Animalia Coleoptera Scarabaeidae

Genus Ceafornotensis gen. n.

Etymology.

From Old English ceafor (chafer) and Greek notius (south).

Type species.

Ceafornotensis archratiras sp. n.

Diagnosis.

The placement of the fossil beetle within the superfamily Scarabaeoidea is based on the following synapomorphies as referred to in Krell (2006); antennae with a lamellate club; pronotum and forelegs adapted for burrowing; protibae dilated apically.

Character comparison.

The specimen differs from Glaresidae , Lucanidae , Passalidae , Trogidae by six visible sternites; from Diphyllostomatidae , Ochodaeidae by partially division of the eye by a genal lobe, apical spurs of the tibae not serrate; from Pleocomidae by developed mouthparts; from Glaphyridae by broad pronotum (not subquadrate), elytra long in form, covering most of the abdomen; from Bolboceratidae , Geotrupidae , Glaphyridae , Hybosoridae by protibia with a single tooth to outer margin, tibia outer margin not serrate, parameres long relative to basal piece and symmetrical to subsymmetrical, median lobe absent or reduced. Additionally, left mandible broad and dentate, not sickle shaped, the form unlikely to accommodate a well-developed mesal brush, antennae lamellae without cupule, would omit the specimen from the Hybosoridae to which the habitas of the specimen otherwise closely resembles.

Of the subfamilies of the Scarabaeidae , the specimen differs from Scarabaeinae, by two spurs on the metatibia, middle coxae contiguous, scutellum well developed; from Aphodiinae, Allidiostomatinae, Orphninae by spurs close-set, not separated by basal tarsomere; from Cetoniinae by short clypeus, not restricted in width before eyes, mandibles broad and dentate, the form unlikely to accommodate a well-developed mesal brush; from Rutelinae by metatarsal claws symmetrical, small, apical tarsomere not enlarged and lengthened; from Dynastinae by pronotum and clypeus simple, lacking major protuberances, foveae or carinae.

The presence of minor pronotal or cephalic armature cannot be discounted and pronounced dimorphic features are not present in all tribes (e.g. Cyclocephalini ) or may exhibit intra-specific variation. From the existing fossil record and divergence time estimates ( Ahrens et al. 2014; Krell 2006), the Dynastinae are thought to have diverged from the Rutelinae during the Palaeogene. On the balance of available evidence the placement of the specimen within the Dynastinae is thought unlikely.

From Mesozoic taxa the specimen differs from Cretoscarabaeinae, Lithoscarabaeidae , Holcorobeini ( Nikolajev 1998) and Cretorabaeus Nikolajev, 1995 ( Nikolajev 1995) by meso-, metatibia bearing a single transverse carina; from the Mesozoic genera of the tribe Sercini ; Lithanomala Nikolajev, 1992 and Cretoserica Nikolajev, 1998 ( Nikolajev 1998) by apical spurs close-set, not separated by basal tarsomere. Nikolajev erected the family Cretomelolonthinae ( Nikolajev 1998; Nikolajev 2007) based on four specimens of Cretomelolontha transbaikalica Nikolajev, 1998, from the Baissa locality, Lower Cretaceous. Although some characters are common to the Orapa specimen; spur at mid and hind tibial apices close-set, mid and hind tibae with one transverse carina, the Baissa specimen possesses features of the wing which cannot be corroborated; wings are not preserved in the Orapa specimen although the form and humeral development would suggest that the beetle was capable of flight. Other characters could be considered plesiomorphic. The Orapa specimen differs by broader tarsomeres relative to the width of the tibial apices, and the longer length of the parameres relative to the basal piece (membrane).

The paucity of apomorphies ( Browne and Scholtz 1998), and that the phylogeny of the Melolonthinae is considered paraphyletic ( Ahrens 2006) and unresolved ( Jameson and Ratcliffe 2000) makes the placement of fossils into this subfamily problematic. However, lack of support for the specimen’s inclusion outside of the 'higher scarabs’ together with relative length of the parameres to the basal piece (Fig. 4c), elongate and narrow antennal lamellae and evidence from the fossil record, give support for the specimen’s placement within the Melolonthinae.

Systematic phylogeny: Phylogenetic analysis was performed using the character set from Bai et al. (2011). Included in the analysis are 20 species comprising 12 families of the Scarabaeoidea, a fossil specimen from Yixian Formation, Prophaenognatha robusta Bai et al., 2011 described in Bai et al. (2011), the Orapa specimen and three outgroup species comprising three families of the Hydrophiloidea ( Hydrophilidae , Histeridae , Synteliidae ). Of the 68 characters in the character set, 27 could be identified with confidence in the Orapa specimen (Table 1). As in Bai et al. (2011), heuristic searches and a bootstrap analysis were performed in Winclada/Nona with the same parameter settings. A strict consensus tree (Fig. 1) was derived from six most parsimonious trees. The phylogeny obtained from the analysis is similar to that in the original study with divisions of higher taxa poorly supported but good support for family groups (see bootstrap values Fig. 1). In the strict consensus tree, the relationship between several families could not be resolved. The Orapa specimen was placed within this polytomy with moderate support as a sister taxa to the Phaenognathini which includes the Yixian fossil Prophaenognatha robusta (Fig. 1). The position of the Orapa fossil in the phylogeny is supported by two character states; antennal club loose, and outer apical angle of protibia simple or slightly produced.

The close relationship between Ochodaeidae and the Hybosoridae , which is supported in both morphological ( Browne and Scholtz 1999; Scholtz et al. 1988) and molecular-based phylogenies ( Ahrens et al. 2014; Smith et al. 2006), was not apparent in the strict consensus tree and may suggest that the placement of Ochodaeidae as a sister taxa to the Phaenognathini is erroneous. The Phaenognathini , recently established by Ocampo and Mondaca (2012), contains the genera Phaenognatha Hope, 1845 and Neophaenognatha Allsopp, 1983 formerly placed within the Aclopinae. The position of the Phaenognathini within the Melolonthinae remains unclear although Ocampo and Mondaca (2012) have hypothesised a relationship between the Phaenognathini and the Lichniini suggesting that they may "constitute a distinct and ancient lineage of Scarabaeidae ". Evidence from a preliminary molecular analysis ( Smith et al. 2006) indicates that several smaller taxa belong within a Melolonthinae clade or ‘grade’. These taxa include Lichniini , removed from the Glaphyridae ( Hawkins 2006), and subfamilies of the Scarabaeidae ; Aclopinae, Allidiostomatinae, Euchirinae, Orphninae and Pachypodinae. The paraphyletic grade of the Melolonthinae is also supported by recent studies ( Ahrens et al. 2014; McKenna et al. 2015). Given the uncertainties of the current phylogeny, the Orapa specimen is placed as Melolonthinae incertae sedis.