Metaxydytes, Miller & Michat & Ferreira Jr, 2024

Miller, Kelly B., Michat, Mariano C. & Ferreira Jr, Nelson, 2024, Reclassification of Cybistrinae Sharp, 1880 in the Neotropical Region (Coleoptera, Adephaga, Dytiscidae), with description of new taxa, ZooKeys 1188, pp. 125-168 : 125

publication ID

https://dx.doi.org/10.3897/zookeys.1188.110081

publication LSID

lsid:zoobank.org:pub:997ADB92-AFA7-4979-82A2-B81C00EF3AEA

persistent identifier

https://treatment.plazi.org/id/99CCA782-DD1A-4DE2-8D5D-F71909BE0E8F

taxon LSID

lsid:zoobank.org:act:99CCA782-DD1A-4DE2-8D5D-F71909BE0E8F

treatment provided by

ZooKeys by Pensoft

scientific name

Metaxydytes
status

gen. nov.

Metaxydytes gen. nov.

Figs 4 View Figures 1–8 , 28 View Figures 15–29 , 29 View Figures 15–29 , 57 View Figures 51–57 , 62 View Figures 62–66 , 69 View Figures 67–71

Megadytes sensu auctorum.

Type species.

Megadytes fraternus Sharp, 1882: 708, by current designation.

Diagnosis.

These species have males with equal-length metatarsal claws and females with two claws of unequal length with the posterior claw distinctly reduced (Figs 28 View Figures 15–29 , 29 View Figures 15–29 ). The medial margins of male sternite IX are linear, not emarginate (Fig. 57 View Figures 51–57 ). This group and Paramegadytes are similar in having females with the medial margins of the gonocoxosternite with a series of spinous setae (Fig. 62 View Figures 62–66 ). From Paramegadytes these species differ in being smaller (≤ 24 mm in Metaxydytes , compared with ≥ 27 mm in Paramegadytes ) and having the metasternal wings relatively narrow (WC/WV = 2.5-2.6 in Metaxydytes , compared with WC/WV = 1.8-1.9 in Paramegadytes ). Third instar larvae have; (1) the median lobe of the frontoclypeus truncate apically with a tuft of setae (Fig. 69 View Figures 67–71 ), (2) the median and lateral lobes of the frontoclypeus separated by a narrow emargination (Fig. 69 View Figures 67–71 ), and (3) the lateral lobes of the frontoclypeus apically simple and acutely angulate (Fig. 69 View Figures 67–71 ).

Etymology.

Metaxydytes is from the Greek metaxy, meaning “between,” and dytes, meaning “diver,” the root word for many genera of Dytiscidae including in this subfamily. The genus is named to signify its intermediate phylogenetic placement among other genera of Cybistrinae .

Phylogenetic relationships.

This genus may be sister group to Paramegadytes based especially on the presence of distinctive stiff, spinous setae along the medial margins of the female gonocoxosternite ( Miller et al. 2007), although in the analyses presented here the group is ambiguously resolved near Nilssondytes , Paramegadytes and Megadytes + Cybister (Figs 75 View Figure 75 , 76 View Figure 76 ).

Discussion.

These species were previous placed in Megadytes . The type species of Megadytes s. str. is M. latus which belongs to a different genus from all other known species previously placed in Megadytes (Figs 75 View Figure 75 , 76 View Figure 76 ) requiring this new name for those species now in Metaxydytes . The species of Metaxydytes have never been completely revised, although Trémouilles (1989a, b) and Trémouilles and Bachmann (1980) addressed the species in southern South America. The genus is in need of a comprehensive revision.

Kingdom

Animalia

Order

Coleoptera

Family

Dytiscidae

Loc

Metaxydytes

Miller, Kelly B., Michat, Mariano C. & Ferreira Jr, Nelson 2024
2024
Loc

Megadytes

Miller & Michat & Ferreira Jr 2024
2024