Cretotaenia pallida Ponomarenko, 1977

Fikáček, Martin, Prokin, Alexander, Angus, Robert B., Pono, Alexander, Marenko, Yue, Yanli, Ren, Dong & Prokop, Jakub, 2012, Revision of Mesozoic fossils of the helophorid lineage of the superfamily Hydrophiloidea (Coleoptera: Polyphaga), Acta Entomologica Musei Nationalis Pragae 52 (1), pp. 89-127 : 99-102

† Cretotaenia pallida Ponomarenko, 1977

( Figs. 14–25 , 63–72 )

Cretotaenia pallida Ponomarenko, 1977a: 93 .

Type locality and age. Russia, Buryat Republic, Baissa outcrops [ river Vitim below the mouth of the Baissa river]. Early Cretaceous, Berriasian to Hauterivian, ca. 146–135 mya ( ZHERIKHIN et al. 1998; Vasilenko, pers. comm. to A. Prokin, 2011)

Material examined (36 spec.). HOLOTYPE: PIN 1989/2890 (piece and counterpiece). PARATYPES: PIN 1989/2889 (piece and counterpiece), PIN 1989/2903 (piece only), PIN 1989/2893 (piece only), PIN 1668/1837 (piece only), PIN 1989/2892 (piece only), PIN 1989/2900 (piece only). ADDITIONAL NON- TYPE SPECIMENS: PIN 4210/589 (piece only), PIN 4210/594 (piece only), PIN 4210/595 (piece only), PIN 4210/596 (piece and counterpiece), PIN 3064/930 (piece and counterpiece), PIN 1989/2887 (piece only), PIN 1989/2902 (piece only), PIN 3064/6847 (piece and counterpiece), PIN 3064/6848 (piece and counterpiece), PIN 3064/6855 (piece only), PIN 3064/6858 (piece only), PIN 3064/6865 (piece only), PIN 3064/6871 (piece only), PIN 3064/6872 (piece only), PIN 3064/6882 (piece only), PIN 3064/6883 (piece only), PIN 3064/6892 (piece only), PIN 3064/6894 (piece only), PIN 3064/6895 (piece only), PIN 3064/6897 (piece only), PIN 3064/6898 (piece only), PIN 3064/6899 (piece only), PIN 3064/6908 (piece only), PIN 3064/6909 (piece only), PIN 3064/6914 (piece only), PIN 3064/6925 (piece only), PIN 3064/6927 (piece only), PIN 3064/6942 (piece only), PIN 3064/6947 (piece only), PIN 3064/6949 (piece only), PIN 3064/6952 (piece only), PIN 3064/6953 (piece only).

Redescription. Body elongate oval, body length 6.2–14.5 mm (holotype 8.8 mm), width of head capsule 0.85–0.97 mm (holotype 0.97 mm). Head hyperprognathous, occipital foramen shifted dorsally. Head capsule slightly widening anteriad, frontoclypeus symmetrical; nasale triangular, epistomal lobes semicircular, slightly overlapping nasale, bearing series of pits (setal articulations) along anterior margin indicating that series of setae was present originally; parietale with darkened stemmatal area bearing 5 stemmata (see the note under generic diagnosis for discussion of the number of stemmata of C. pallida ), posterior portions of parietale darkened; frontal sulci V-shaped, coronal sulcus probably at most very short. Antenna probably attaching on dorsal head surface, scape longer than pedicel. Mandible large, falcate, with two retinacular teeth, distal one larger than proximal one. Maxillae longer than mandibles. Labium not projecting far anteriad, without ligula, labial palpi rather short. Hypostomal sclerite subtrapezoid. All thoracic segments largely sclerotised dorsally, tergites subdivided by a fine median suture; thoracic pleura not sclerotised. Abdominal segments 1–8 each with a pair of large dorsal sclerites, each pleuron with two minute sclerites situated above spiracle; spiracles open, tracheal system holopneustic with large tracheal trunks; abdominal segment 9 with single dorsal sclerite, bearing large 3-segmented urogomphi.

Note. PONOMARENKO (1977a) mentioned that two size categories may be distinguished in the material available to him at the time of the description. Several dozens of additional specimens were collected in Baissa outcrops since that time (of which only better preserved specimens examined in detail for this study are listed above). We have measured body length and head width (measured as the distance between lateralmost portions of dark ocular area) of 19 wellpreserved specimens ( Table 1). Body length is highly variable among the specimens as the larvae were probably macerated to variable extent before fossilization and their membranous parts (especially the abdomen) were deformed. In contrast, head width shows a tendency to fall into three size categories with prevailing values of 0.87 mm, 0.91 mm and 0.97 mm ( Fig. 26 ). Although the distinctness of these categories cannot be tested due to the low number of specimens available, the measurements seem to indicate that three larval instars were present in C. pallida . This corresponds with the presence of three larval instars known for the vast majority of modern Helophorus species (the only exceptions are two species inhabiting semidesert areas in which only two instars are present corresponding to the first and third instar of the species with normal living cycle; ANGUS 1992, 1998).

Figures

Figs. 14–18. Cretotaenia pallida Ponomarenko, 1977 (details of the head). 14 –PIN 3064/6899; 15 – PIN 4210/595; 16 – PIN 3064/6898; 17 – PIN 3064/6848, detail of the head in dorsolateral position; 18 – PIN 3064/6872, detail of right mandible and nasale. Scale bars: 2 mm. Abbreviations: ant – antenna; epl – epistomal lobe; lb – labium; md – mandible; mx – maxilla; ocf – occippital foramen.

Figs. 19–25. Cretotaenia pallida Ponomarenko, 1977. 19 – PIN 3064/6848, larva in dorsolateral position; 20 – PIN 1989/2890 (holotype), general view; 21 – PIN 3064/6883, head, thorax and abdominal segments 1–2; 22 – PIN 1989/2900, urogomphi; H: 23 – PIN 3064/6871, urogomphi; 24 – PIN 3064/6953, urogomphi; 25 – PIN 3064/6897, urogomphi.Scale bars: 1 mm.Abbreviations: msth – mesothorax; mtth – metathorax; prth – prothorax; sp – spiracle; ur – urogomphus.

Figs. 63–72. Cretotaenia pallida Ponomarenko, 1977. 63 – PIN 1989/2890 (holotype), general view; 64 – PIN 3064/6848, detail of the head in dorsolateral view; 65 – PIN 3064/6872, detail of anterior portion of the head; 66 – PIN 3064/6899, head and prothorax; 67 – PIN 3064/6883, head, thorax and abdominal segments 1–2; 68 – PIN 4210/595, detail of the head; 69 – PIN 3064/6848, detail of abdominal segments in lateral view; 70 – PIN 3064/6871, urogomphi; 71 – PIN 1989/2900, urogomphi; 72 – PIN 3064/6897, urogomphi. Scale bars: 0.5 mm.

Fig.26.Frequency histogram of head width of the examined specimens of Cretotaenia pallida (n = 15).