Mathesius liaoningensis

Kolibáč, Jiří & Huang, Di-Ying, 2011, Mathesius liaoningensis gen. et sp. nov. of Jehol Biota, a presumptive relative of the clerid or thaneroclerid branches of Cleroidea (Coleoptera), Zootaxa 2872, pp. 1-17 : 6-15

Classification of Mathesius liaoningensis gen. et sp. nov.

The identification tool “Beetles of the World” by Lawrence et al. (1999) was used for the first analysis of character states. The “Best character” feature was used for a preliminary selection of recent beetle higher taxa, potentially relative to Mathesius liaoningensis gen. et sp. nov. Only the characters which were clearly visible in the fossil were taken into consideration. The features “Diagnose” and “Describe” were used for a comparison of selected characters among families.

The following characters unambiguously classify the fossil among Cleroidea:

1. Aedeagus (type): cucujiform.

2. Mesotarsus (number of distinct and reduced tarsomeres): with 5 distinct tarsomeres (= pentamerous).

3. Mesocoxal cavities at middle: narrowly separated.

4. Metacoxae (whether extending laterally to meet elytra or sides of body): extending laterally to meet elytra or sides of body.

5. Antennae (type): incrassate or clavate.

Note. When the character state “Number of abdominal ventrites: 6” is used instead of “Antennae (type)”, Acanthocnemidae , Cleridae (incl. Thanerocleridae , Metaxinidae in Lawrence et al. 1999), Melyridae and some Trogossitidae are selected. When the number of abdominal ventrites is used as the point 1, the number of steps to Cleroidea is lower than five. It is explained above (Species description: Remarks, point 5) why we did not use it as a primary character. However, it also strongly supports a classification of the fossil within Cleroidea. The first character (aedeagus cucujiform) is variable among Cleridae , Thanerocleridae and Melyridae sensu lato: the basal form is “with single strut and opposing paired struts”, but struts are reduced in some advanced members, therefore, the tegmen resembles the “tenebrionoid” type (e.g., in all Thanerocleridae , Malachiinae ). The state “Antennae incrassate or clavate” excludes Trogossitidae from a selection, the number of ventrites (= 6 in the fossil) excludes Chaetosomatidae (with 5 ventrites).

The following characters of the fossil exclude the melyrid branch and only Cleridae (incl. Thanerocleridae and Metaxinidae ) remains:

1. Prosternal process: strongly and abruptly expanded at apex. (or) 2. Frontoclypeal suture: distinctly impressed.

Note. The fossil resembles the extant Cleridae with the tarsomeres 1–4 (or at least 2–3) lobed. There are distinct lobes in strongly dilated protarsomeres 1–4 in all known modern thaneroclerids, however, these tarsomeres are not lobate in meso- and metatarsi; their tarsomeres can be very weakly dilated only or bearing lobe-like brush of rigid setae along the apices of ventral side of particular tarsomeres. The lobes are absent in all pairs of the tarsi in Chaetosomatidae and Metaxinidae but always present in Cleridae . The fourth meso- and metatarsomeres are probably a little shorter than the third ones; it somewhat resembles a structure of tarsi in the subfamily Korynetinae (Cleridae) . For a review of dignostic characters among Mathesius liaoningensis gen. et sp. nov. and major cleroid families see Tab. 1.