Pseudolonchodina, Zhou, Zhai, and Xian, 1981

Waid, Christopher B. T. & Cramer, Bradley D., 2017, Telychian (Llandovery, Silurian) conodonts from the LaPorte City Formation of eastern Iowa, USA (East-Central Iowa Basin) and their implications for global Telychian conodont biostratigraphic correlation, Palaeontologia Electronica 42 (6), pp. 1-37 : 27-28

Pseudolonchodina sp. n.

Figure 8.1 -12, 8.19

Description. Sa elements alate. Lateral processes denticulate and recurved in aboral view. Denticles closely spaced, evenly sized, compressed, and slightly curved posteriorly. Cusp reclines at a sharper angle than denticles. Highly compressed basal cavity extended posterior to the cusp. Sb elements tertiopedate. Denticulate lateral processes extend down from the cusp at slightly different angles. Denticulate, compressed posterior process inclined towards one of the lateral process. Basal cavity compressed, and extends along most of the lateral processes and along the posterior process. Sc elements bipennate. Anterior process denticulate and angled inwards. Denticulate posterior process extends straight behind cusp. M elements have a large posteriorly reclined and inwardly inclined cusp. Posterior process bowed with five to seven denticles. Basal cavity bowed in with the same geometry as the posterior process. Pb elements digyrate. Lateral processes twisted and bowed to different degrees in different specimens. Outer lateral process extends slightly down and away from cusp. Inner lateral process extends away from cusp. Denticles are compressed, closely spaced, and slightly curved posteriorly. Pa elements digyrate. Lateral processes extend away from cusp at slightly different angles. Processes not as twisted and bowed as those on Pb elements. Basal cavity compressed and extended along lateral processes. In most of the specimens recovered, white matter extends down below the denticles and is separated from the white matter of adjacent denticles by translucent material. Denticles are not fused in most speciemens for all element types. In a minority of M and Sc element specimens, the denticles farthest away from the cusp are slightly fused (e.g., Figure 8.7, 8.10 ).

Remarks. The Sc elements are almost indistinguishable from those of Wurmiella polinclinata . Some of the elements identified as occupying the Sc position of Pseudolonchodina sp. n. may actually be juvenile S 3/4 elements of Wurmiella? polinclinata , which could be a reason for the overrepresentation of Pseudolonchodina Sc elements.

The general shape and many of the characteristics of our specimens are similar to specimens classified as Pseudolonchodina fluegeli ( Walliser, 1964) . However, the discrete (non-fused) denticles on our Pa specimens provides a consistent character for distinguishing our specimens from the wide range of morphologies attributed to Psl. fluegeli (Walliser) .

The species concept of Psl. fluegeli is extremely broad, partially due to a lack of a multielement apparatus reconstruction using Walliser’s type material ( Wang and Aldridge, 2010). There have been numerous reconstructions of fluegeli by various authors (e.g., Aldridge, 1979; Savage, 1985; Bischoff, 1986; Over and Chatterton, 1987; Armstrong, 1990), each using specimens from different regions and chronostratigraphic levels. The apparatus reconstructions and element descriptions of Bischoff (1986; as Oulodus planus planus ) and Armstrong (1990; as Aspelundia fluegeli ) are the most complete, and the most widely followed in subsequent conodont research (e.g., Wang and Aldridge, 2010). The position of elements in their apparatus reconstructions are similar, but their Pa and Pb elements are switched, and Armstrong added a bipennate Sb element to the apparatus (termed Sb 2) and suggested that the apparatus might also include an Sd element ( Armstrong, 1990, p. 53-54). There are also differences between Bischoff (1986) and Armstrong (1990) in the degree of fusion of the denticles on most element types. Bischoff (1986) describes the denticles on Pb, M, and Sb as basally confluent (slightly fused), denticles on Sa and Sc as discrete, and denticles on Pa elements as fused to mid-height. In contrast, Armstrong (1990) describes denticles as partially fused on Pb (= Pa of Bischoff, 1986) elements, and fused to mid-height on M elements and the anterior process of Sc elements.

Some attempts have been made to distinguish different morphologies of Psl. fluegeli s.l. as subspecies. Bischoff (1986) erected Oulodus planus planus and the stratigraphically higher Oulodus planus borenorensis based on characteristics of Sb and Sc elements. The Sb elements of Ou. planus borenorensis have a shortened lateral process bearing one large and one or two small denticles. The Sc element of Ou. planus borenorensis is characterized by the presence of an elongated anterior process on Sc elements bearing 8–11 tall denticles and a posterior process with posteriorlyreclined denticles that increase in size away from the cusp.

Männik (2007a) separated Aspelundia? fluegeli ssp. n. from Asp? fluegeli fluegeli based primarily on the height and fusion of denticles, and the distribution of white matter below the denticles. Asp? fluegeli ssp. n. is characterized by tall, thin denticles that are fused up to mid-height, whereas the denticles of Asp? fluegeli fluegeli are wider and more rubust, and fused in their lower halves (Männik, 2007, p. 57; Männik, personal commun., 2016). The white matter below the denticles of Asp? fluegeli ssp. n. is separated by rectangular blocks of translucent material, and the white matter of Asp? fluegeli fluegeli is only separated by thin strips of translucent material ( Männik, 2007a, figure 10). The fusion of the denticles in both subspecies of Asp? fluegeli sensu Männik is very different from that of Bischoff (1986) and Wang and Aldridge (2010), where the denticles of all element types except for Pa elements are only slightly fused or discrete. Asp? fluegeli fluegeli sensu Männik is somewhat more similar to the specimens described in Armstrong (1990), which contains elements with denticles fused to mid-height. However, to further muddy the taxonomic waters of this species, the Sa and Sb elements of Asp? fluegeli sensu Männik do not have posterior processes (Männik, personal commun., 2016). The Sa and Sb elements of Bischoff (1986), and the Sa and Sb 1 elements of Armstrong (1990) are tertiopedate, thus making it likely that Asp? fluegeli sensu Männik is a separate taxon from Psl. fluegeli s.l. altogether.

Material examined. Eight Sa, twelve Sb, thirty Sc, twelve M, ten Pb, two Pa elements.

Figures

FIGURE 8. Conodonts from the Garrison Core. 1-12, 19, Psuedolonchodina sp. n., Sa element, posterior view, GC 115.51–115.76 m, SUI 152266 (1); Sa element, posterior-aboral view, GC 121.62–121.88 m, SUI 142267 (2); Sb element, anterior view, GC 134.06–134.31 m, SUI 142268 (3); Sc element, lateral view, GC 130.20–130.48, SUI 142269 (4); Sc/M? element fragment, lateral view, GC 128.85–129.11 m, SUI 142270 (5); M element, lateral-posterior view, GC 131.95–132.23 m, SUI 142271 (6); M element, anterior-lateral view, GC 134.06–134.31 m, SUI 142272 (7); Pa element, oral view, GC 134.06–134.31 m, SUI 142273 (8); Pa element, oral view, GC 130.79–131.09m, SUI 142274 (9); Sc element, lateral view, GC 135.65–136.10 m, SUI 142259 (10); Pb element, lateral, and lateral-aboral views, GC 115.51–115.76 m, SUI 142275 (11 and 12); and Pb element, lateral view, GC 130.79-131.09 m, SUI 142276 (19). 13, 15, Oulodus sp. indet., Sa element, anterior-lateral view, GC 137.12–137.40 m, SUI 142277 (13) and Pa element, posterior view, GC 135.65–136.10 m, SUI 142278 (15). 14, 16-17, Oulodus cf. Ou. petilus pacificus, Sc element, lateral view, GC 134.06–134.31 m, SUI 142279 (14); Sb element, posterior-oral view, GC 130.20–130.48 m, SUI 142280 (16); and Pb element, anterior-lateral view, GC 130.79–131.09 m, SUI 142281 (17). 18, 21-22, Distomodus staurognathoides, Sb element, posterior view, GC 134.06–134.31 m, SUI 142282 (18); Pa element, oral view, GC 135.65– 136.10 m, SUI 142283 (21); and Pa element, oral view, GC 135.65–136.10 m, SUI 142282 (22). 20, Aulacognathus angulatus, P2 element, lateral view, GC 135.65–136.10 m, SUI 142285.