Polonodus newfoundlandensis Stouge, 1984
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https://doi.org/ 10.3853/j.0067-1975.63.2011.1586 |
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https://treatment.plazi.org/id/03CCEB77-FFCE-6353-FC3E-FA099650F9F0 |
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Felipe |
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scientific name |
Polonodus newfoundlandensis Stouge, 1984 |
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Polonodus newfoundlandensis Stouge, 1984
Fig. 17A–K View Figure 17
Polonodus newfoundlandensis Stouge, 1984: 73–74 , pl. 13, figs 14–16, text-fig. 28.
Polonodus cf. newfoundlandensis Stouge. –Zhao et al., 2000: 215, pl. 30, figs 16–17.
Polonodus kunshanensis Ding in Wang, 1993: 191, partim, only pl. 33, fig. 17, non figs 15, 18 =? Dzikodus tablepointensis .
? Polonodus sp. Gao, 1991 : partim only pl. 9, figs 8–9,?13.
Material. 36 specimens from one sample at the top of the Dawangou Formation ( Table 2).
Remarks. Stouge (1984) erected P. newfoundlandensis as consisting of a bimembrate apparatus including paired (in mirror image) Pa (polyplacognathiform) and paired Pb (ambalodiform) elements, and suggested that it differed from the type species, P. clivosus in having smaller denticles on the anterior process of the Pb element and in having a deeper inner notch on the anterior process. The holotype is a sinistral Pa element from the lower part of the Table Head Formation (A3, H. holodentata Zone ) of western Newfoundland ( Stouge, 1984).
Only pectiniform P elements have been recovered in our material from the Dawangou Formation. The Pa element ( Fig. 17A–D View Figure 17 ) shows some features intermediate between P. newfoundlandensis and P. clivosus (Viira, 1974) . It is comparable with the holotype of P. newfoundlandensis in having a prominent notch on the inner side of the anterior process. However, the denticle row on the anterior process of the Pa element from Dawangou is more strongly curved inner laterally than that of the holotype, a feature that is more comparable with the specimen that Stouge (1984, pl. 13, fig. 13) referred to as P. clivosus . The Pb element of the Dawangou material ( Fig. 17E–K View Figure 17 ) is comparable with the type material in having small denticles on a narrower platform of the anterior process, but the angle between the denticle rows on the outer lateral process and the anterior process is more acute (around 50°) and the denticle row on the inner lateral process forms an acute angle with that on the posterior process ( Fig. 17F View Figure 17 ) rather than a right angle as in the type material ( Stouge, 1984, pl. 13, fig. 15). In some of the Dawangou specimens, a weak secondary row with several low nodes may also be developed on the posterior lobe ( Fig. 17J View Figure 17 ).
No ramiform S and geniculate M elements have been recognized for P. newfoundlandensis in the literature. However, one specimen of a quadriramate element from the same sample (AFT-X-K13/13) is nearly symmetrical, with denticulate anterior and posterior processes, and an adenticulate, blade-like costa on each lateral side. This specimen, assigned herein as gen. et sp. indet. ( Fig. 17N–O View Figure 17 ), possibly represents the Sd element of P. newfoundlandensis .
An incomplete pectiniform specimen recovered from the same sample (AFT-X-K13/13) has a robust, laterally compressed cusp, a long anterior process with a row of node-like denticles, a short (possibly broken) posterior process, and an outer lateral process with a denticle row forming an angle of about 30° with that on the anterior process ( Fig. 17P–Q View Figure 17 ). Likely a Pb element, it is morphologically different from the Pb element of P. newfoundlandensis associated in this sample from the top of the Dawangou Formation, and is therefore referred to herein as Polonodus sp. A .
The three illustrated specimens of Polonodus kunshanensis Ding in Wang, 1993 represent poorly preserved Pa (polyplacognathiform) elements recovered from the Guniutan Formation of Kunshan, Jiangsu Province. Zhang (1998c) considered this species to be a junior synonym of Dzikodus tablepointensis ( Stouge, 1984) . However, the holotype (Wang, 1993, pl. 33, fig. 18) is badly preserved with distal parts of the processes broken off, making its identification at the species level almost impossible. The illustrated paratype (Wang, 1993, pl. 33, fig. 15) seems comparable with the dextral Pa element of D. tablepointensis illustrated by Zhang (1998c, pl. 7, fig. 6) from the Guniutan Formation of Hunan Province, South China, but the other figured specimen (Wang, 1993, pl. 33, fig. 17) with the posterior process broken off can be well compared with both the material from the Dawangou Formation and the holotype of P. newfoundlandensis from the Table Head Formation of western Newfoundland ( Stouge, 1984, pl. 13, fig. 16), in having a prominent notch between the anterior process and the secondary inner lateral process, and in having the inner lateral process posteriorly curved.
Tarim specimens illustrated as P. cf. newfoundlandensis by Zhao et al. (2000, pl. 30, figs 16–17) exhibit a more prominent cusp in comparison with the Dawangou material and the types from western Newfoundland .
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Polonodus newfoundlandensis Stouge, 1984
| Zhen, Yong Yi 2011 |
Polonodus newfoundlandensis
| Stouge, S 1984: 74 |