Leposida ponomarenkoi, Kotov, 2007
|
publication ID |
https://doi.org/ 10.1080/00222930601164445 |
|
persistent identifier |
https://treatment.plazi.org/id/03B68794-316B-FF97-FE3E-FCC6B02F8DF1 |
|
treatment provided by |
Carolina |
|
scientific name |
Leposida ponomarenkoi |
| status |
sp. nov. |
Leposida ponomarenkoi sp. nov.
( Figures 2 View Figure 2 D–K, 3)
Etymology
This species is dedicated to Dr A. G. Ponomarenko, leader of the expedition of PIN to Unda, where this animal was collected. He participated greatly in forming the crustacean collection of PIN and consulted me on many issues of palaeontology.
Type locality
Clalunikha.
Material studied
Holotype: a specimen in antero-lateral position, 1.9 mm length, PIN 4042 View Materials /60 ( Figures 2D View Figure 2 , 3A, B) . Paratypes: eight specimens on six rock fragments, PIN 4042 View Materials /61–69.
Other material studied. Unda: 10 specimens, PIN 3015 View Materials /2415–2424.
Diagnosis
As for the genus.
Description
Body very high, height/length 5 about 0.9–1.1, rounded (the animal was likely sub-globular), with strongly convex dorsal margin, without postero-dorsal angle, postero-ventral angle widely rounded ( Figures 2E View Figure 2 , 3 C–E). Head massive, about 0.4 body length, with a head shield, its distalmost extremity protruding ventrally. On some impressions there is a line seeming to be a posterior head border ( Figure 3D). In the holotype, there is an indistinct spot in the posterior portion of the head which may be the trace of a large, subovoid dorsal organ ( Figure 2D View Figure 2 , arrow). Head shield wide (with width more than length), its lateral portion covering basis of AII. Valve without marginal setae. Postabdomen massive ( Figure 2E, F View Figure 2 ), with well-defined distal margin as in some recent anomopods, i.e. Bosmina or alonine Nicsmirnoυius ( Kotov 1996; Van Damme et al. 2003; Kotov and Sanoamuang 2004). Postabdominal claw thin, regularly bent.
Antenna I not found. AII thin and long, length from base to tip of exopod slightly less than body length. Basal segment strong, thick. Both antennal branches long, thin, foursegmented, exopod longer than endopod. Exopod ( Figures 2 View Figure 2 G–K, 3B) with first segment small, lacking setae, second to fourth segments elongated, each with a series of setae (but bad preservation does not allow their number to be counted in the majority of specimens), length of second segment more than that of third plus fourth segments. Endopod with small first segment, lacking setae, second segment large, third and fourth segments smaller. I saw only a distal seta on the second segment, a distal seta on the third segment, and three apical setae on the fourth endopod segment, but there is a chance that the animal possessed more setae, which were lost. So, approximate antennal formula (0)-(Ḳ10)-(Ḳ6)-(Ḳ6)/(0)- (1?)-(1?)-(3?). No spines were found on any segments. Mandibles small. In some impressions, unclear outlines of serially similar thoracic limbs (> 5) can be observed ( Figure 3C, D), but no setae were seen. Eggs were not found.
Size 1.8–2.4 mm.
Comments
Unfortunately, preservation of fossils from Chalunikha and Unda is weak compared to those from Ust’-Baley. I did not find any evidence of the presence of more than one species in each locality. Also, I did not find any differences between specimens from the two localities, so I placed cladocerans from Unda in the same species, although I did not include them in the type series of L. ponomarenkoi sp. nov.
Due to moderate preservation of the specimens from Chalunikha and Unda, I have doubts that Leposida gen. nov. really lacked lateral setae on segments 2–4 of endopod, the latter was less preserved than the exopod in all specimens. It is possible that the endopod of Leposida gen. nov., sp. nov. was of the Leptodorosida - type.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.