Lethocerus vetus, Nel, André & Waller, Alain, 2006

Nel, André & Waller, Alain, 2006, A giant water bug from the Lower Cretaceous Crato Formation of Brazil (Heteroptera: Belostomatidae: Lethocerinae), Zootaxa 1220, pp. 63-68 : 64-68

Lethocerus vetus sp. n.

(figs 1–4)

Material

Holotype i 9560, Museo Civico di Storia Naturale di Milano, Italy, paratype MNHN­ LP­R 63882, Muséum National d’Histoire Naturelle, Paris.

Etymology

After the great antiquity of this species.

Age and outcrop

Nova Olinda Member, Crato Formation, Late Aptian, Early Cretaceous, unspecified quarry between Nova Olinda and Santana do Cariri, Ceará, northeast Brazil.

Description

Holotype: body 44 mm long, 17 mm wide; head triangular, 6 mm long, 7 mm wide; mouthpart and antennae not visible, probably hidden under head, compound eyes 2 mm apart, 1 mm diameter.

Thorax not clearly visible, 18 mm long, 15 mm wide.

Fore leg partly hidden under body, femur 10 mm long, 2 mm wide, tibia curved, apex missing; mid leg nearly completely hidden under body; hind femur 13 mm long, 2 mm wide, tibia laterally compressed, 11 mm long, 2 mm wide, two tarsal segments visible, laterally compressed, basal tarsomere 2.5 mm long, 1 mm wide, distal tarsomere 2 mm long, 0.8 mm wide, apical claw 1 mm long. Wings not visible, absent or, if present, probably hidden by body.

Abdomen 21 mm long, 17 mm wide; siphon 6 mm long; abdominal sternites V–VI subdivided laterally by a suturelike fold; spiracle adjacent to mesal margins of ventral laterotergites.

Paratype: same dimensions and body structures as for the holotype; the fore wings are partly preserved (corium), covering the abdomen.

Discussion

This fossil is an adult or a last instar, because of its large size. Its short but distinct air strap and general appearance are closely similar to those of a modern Lethocerus and support an attribution to the Belostomatidae rather than to any other recent or fossil nepomorphan family ( Polhemus 2000). Lauck & Menke (1961) divided the Belostomatidae into three subfamilies on the basis of the structure of the antennal segments and abdominal sternites and spiracles. Later, Lee (1991) also considered the male genitalia, not available in Lethocerus vetus sp. n. Nevertheless, our belostomatid bug can be attributed to the subfamily Lethocerinae Lauck & Menke, 1961 ( Lethocerus Mayr, 1853 ) on the basis of its abdominal sternites V–VI subdivided laterally by a suturelike fold and the spiracles adjacent to the mesal margins of the ventral laterotergites ( Lauck & Menke 1961: 646). Furthermore, the placement of L. vetus sp. n. in the Lethocerinae is supported by one apomorphy ’Metatibien und — tarsen sehr stark abgeflacht und dadurch dünn erscheinend’, i.e., the metatibia and tarsus are laterally compressed and flat and thus appear weak ( Mahner 1993: 63). Its attribution to the genus Lethocerus sensu stricto is only based on its general similarity with the modern representatives of this genus.

Among the fossil Belostomatidae that could be related to the Lethocerinae , Nel & Paicheler (1992) considered Sinobelostoma liui Chou & Hong, 1989 from the Early Cretaceous of China, a belostomatid of uncertain subfamily that could belong to the Lethocerinae . This taxon is poorly characterized, but it is smaller than L. vetus sp. n. (body 30 mm long, instead of 45 mm) ( Chou & Hong 1989). Popov (1971, 1992) considered the Late Jurassic Mesobelostomum deperditum (Germar, 1839) might be a lethocerine, but Nel & Paicheler (1992) indicated that this taxon is rather poorly known and of uncertain subfamily. It differs from L. vetus sp. n. in its longer body (55 mm long). The body of the Middle Jurassic Aenictobelostoma Polhemus, 2000 is clearly more rounded and shorter than that of L. vetus sp. n. ( Polhemus 2000).

Among the Belostomatidae from the Crato Formation, Neponymphes godoii Zamboni, 2001 differs from L. vetus sp. n. in its more rounded body and distinctly smaller size ( Zamboni 2001). Araripebelostomum martinsnetoi Nel & Paicheler, 1992 is also distinctly shorter than L. vetus sp. n., with a more rounded body ( Nel & Paicheler 1992).

We attribute L. vetus sp. n. to the genus Lethocerus because it has no perceptible difference from the Recent representatives of this genus. Such morphological stability suggests that it had a similar way of life, as a predator on small fishes and invertebrates.

References

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