Pteropelta gladiata Eisenack, 1939

Hints, Olle & Eriksson, Mats E., 2010, Ordovician polychaeturid polychaetes: Taxonomy, distribution and palaeoecology, Acta Palaeontologica Polonica 55 (2), pp. 309-320 : 313

Pteropelta gladiata Eisenack, 1939

Fig. 1 .

1939 Pteropelta gladiata sp. nov.; Eisenack 1939: 164, pl. C: 2.

1939 Pteropelta glossa sp. nov.; Eisenack 1939: 164, pls. B: 1, C: 2–3.

1939 Pteropelta thompsoni sp. nov.; Eisenack 1939: 165, pl. B: 3.

1956 Polychaetura gracilis sp. nov.; Kozłowski 1956: 192–195, figs. 17–18.

1956 Polychaetura sp. a; Kozłowski 1956: fig. 19.

1966 Polychaetura gracilis Kozłowski ; Kielan−Jaworowska 1966: 103– 105, pls. 22, 23: 3–7, text−fig. 8L.

1982 “Zusammengesetzte Maxille links”; Schallreuter 1982: pl. 2: 5.

1996 Polychaetura gracilis Kozłowski ; Szaniawski 1996: pl. 2: 6.

1998 Polychaetura gracilis Kozłowski ; Hints 1998: 496, fig. 12A–D.

2000 Pteropelta gladiata Eisenack ; Hints 2000: pl. 2: 3–4.

2007 Pteropelta gladiata Eisenack ; Hints and Eriksson 2007a: fig. 4F–G.

2009 Pteropelta gladiata Eisenack ; Eriksson and Hints 2009: fig. 5k–l.

Type material: Holotype: carriers figured by Eisenack 1939: pl. C: 2

(specimen lost), neotype: apparatus ( ZPAL Sc 0/1/1) figured by Kozłowski 1956: fig. 17 .

Type locality and horizon: Erratic boulder No. 0.116 of Baltic origin,

Upper(?) Ordovician age, collected from Wyszogród, Poland.

Remarks.—This species has been described in detail by Kozłowski (1956) and subsequently also by Kielan−Jaworowska (1966). In one of the articulated apparatuses recovered ( Fig. 1U ) we discovered anterior maxillae with an unusual morphology. At least the right MII, but possibly also the MIV and the left MII appear to be composed by lamella−like plates, each one terminating dorsally into a denticle. Similarly, Kielan−Jaworowska (1966: 104–105) noted in the description of Polychaetura gracilis that the boundaries between the denticles of the anterior maxillae are prolonged along the entire width of the jaw and (for the left MIII) that the jaw becomes separated into individual denticles. Such type of anterior maxillae is characteristic of Tretoprion astae Hints, 1999 and may suggest a relationship between the Polychaeturidae and Tretoprionidae (see also discussion of Pteropelta kielanae below).

Based on the extensive collections from Estonia Pteropelta gladiata is the only polychaeturid species, which has incised posterior margin in left MI and concave (incised) anterior margins of carriers.

The variability of P. gladiata is relatively wide concerning both size (cf. Fig. 1O and J 1 ) and general morphology of the posterior maxillae (see for example specimens in Fig. 1C and D which are from the same sample). In addition, there is a notable morphological trend within the lineage. In the left MI this concerns the inner wing, which is relatively wider in Darriwilian to early Katian specimens ( Fig. 1A–G ) compared to younger material ( Fig. 1H, I ). Generally, the right MI becomes more elongated with a longer shank and reduced ramus (cf. Fig. 1L and P ). Like Kielan−Jaworowska (1966) we consider these differences to fall within the intraspecific variability. It should be added that the proposed neotype represents the older morphotype of the species.

Stratigraphic and geographic range.—Volkhov to Juuru regional stages (Darriwilian to basal Llandovery) of Baltoscandia ( Estonia, NW Russia, Sweden, Poland), Baltic erratic boulders, upper Richmondian (Katian) of Ohio, USA; possibly Ordovician(?) of Kazakhstan.

Figures

Fig. 1. Elements of jaw apparatuses of Ordovician polychaeturid polychaete Pteropelta gladiata Eisenack, 1939. A–I. Left MI, all in dorsal view. A. GIT 592−34, sample OM97−5, Väike−Pakri Cliff, Estonia, Kunda Stage, Darriwilian. B. GIT 592−35, sample OM97−20, Väike−Pakri Cliff, Estonia, Uhaku Stage, Darriwilian. C. GIT 592−36, sample OM03−51, Viru Mine, Estonia, Kukruse Stage, Sandbian. D. GIT 433−24, sample OM03−51, Viru Mine, Estonia, Kukruse Stage, Sandbian. E. GIT 592−37, sample OM97−116, Väike−Pakri Island, Estonia, Kukruse Stage, Sandbian. F. GIT 592−38, sample OM−205, Vaemla F−364 borehole, 140 m, Estonia, Keila Stage, Sandbian. G. GIT 592−39, sample M96−81, Orjaku borehole, 112.5 m, Estonia, Rakvere Stage, Katian. H. GIT 592−40, sample M96−1, Laeva 18 borehole, 187.45 m, Estonia, Pirgu Stage, Katian. I. LO 10476, sample 04E1−3, Stormyr−2 borehole, 213.65 m, Sweden, Pirgu Stage, Katian. J–Q. Right MI, all in dorsal view. J. GIT 433−25, sample OM03−51, Viru Mine, Estonia, Kukruse Stage, Sandbian, magnified (J1) and reduced to the same scale as O, to show size variation (J2). K. GIT 592−41, sample OM03−51, Viru Mine, Estonia, Kukruse Stage, Sandbian. L. GIT 592−42, sample OM−205, Vaemla F−364 borehole, 140 m, Estonia, Keila Stage, Sandbian. M. GIT 592−43, sample M96−49, Orjaku borehole, 47.62 m, Estonia, Pirgu Stage, Katian. N. GIT 592−44, sample M96−49, Orjaku borehole, 47.62 m, Estonia, Pirgu Stage, Katian. O. GIT 592−45, sample D−102/22, Lelle D−102 borehole, 141.42 m, Estonia, Pirgu Stage, Katian. P. GIT 592−46, sample D−102/49, Lelle D−102 borehole, 146.18 m, Estonia, Vormsi Stage, Katian. Q. LO 10477, sample 04E1−3, Stormyr−2 borehole, 213.65 m, Sweden, Pirgu Stage, Katian. R. Left MI, ventral view, GIT 592−47, sample OM97−5, Väike−Pakri Cliff, Estonia, Kunda Stage, Darriwilian. S. Left MI, left lateral view, GIT 592−48, sample M96−81, Orjaku borehole, 112.5 m, Estonia, Rakvere Stage, Katian. T. Right MI, right lateral view, GIT 592−49, sample M96−81, Orjaku borehole, 112.5 m, Estonia, Rakvere Stage, Katian. U. Apparatus, GIT 592−50, sample M−4711, Suhkrumägi outcrop, Estonia, Kunda Stage, Darriwilian. V. Apparatus, GIT 592−51, sample M−4430, Orjaku borehole, 135.6 m, Estonia, Keila Stage, Sandbian/Katian. W. Basal plate, GIT 592−52, sample M−4711, Suhkrumägi outcrop, Estonia, Kunda Stage, Darriwilian. X. Carriers, GIT 315−34, sample M96−77, Orjaku borehole, 63.8 m, Estonia, Pirgu Stage, Katian. Y. Carriers, GIT 592−53, sample M96−49, Orjaku borehole, 47.62 m, Estonia, Pirgu Stage, Katian. SEM micrographs, scale bars 100 µm.