Gyrolepis sp.

Gyrolepis sp.

( Figure 4 View FIGURE 4 D-H)

Specimens referred. NHMD–1811677 – tooth;

NHMD–1811678 – ganoid scale; NHMD–1811679

– ganoid scale; NHMD–1811752 – ganoid scale;

NHMD–1811771 – ganoid scale; NHMD–1811772

– ganoid scale; NHMD–1811773 – ganoid scale;

NHMD–1811774 – ganoid scale; NHMD–1811775

– ganoid scale; NHMD–1811777 – ganoid scale;

NHMD–1811778 – ganoid scale; NHMD–1811779

– ganoid scale; NHMD–1811794 – ganoid scale;

NHMD–1811795 – ganoid scale; NHMD–1811796

– ganoid scale; NHMD–1811800 – ganoid scale;

NHMD–1811781 – ganoid scale; NHMD–1811782

– ganoid scale; NHMD–1811783 – ganoid scale;

NHMD–1811784 – ganoid scale; NHMD–1811785

– ganoid scale; NHMD–1811786 – ganoid scale.

Locality. From site 62/91/G, western side of Tait

Bjerg, Jameson Land, East Greenland (71°28´34´´

North 22°40´43´´ West).

Horizon and age. Thin bone bed in Carlsberg

Fjord Member of the Ørsted Dal Formation in the

Fleming Fjord Group. Late Triassic (Norian).

Description. 22 specimens have been assigned to

Gyrolepis sp. including teeth and two different morphotypes of scales.

Teeth ( Figure 4D View FIGURE 4 ): The teeth are conical, weakly curved, and circular in cross-section. They range in height from around 1 to 1.5 mm. The acrodin cap corresponds to 10% of the tooth total height and is separated from the shaft by a horizontal ridge. The cap is smooth and translucent. Its tip is rounded, but it can be slender and curved. The shaft can have fine vertical striations, but the best-preserved tooth has a smooth shaft and is curved. The base is starlike shaped in cross-section due to grooves at this level, giving the base a flared appearance.

Scale Morphotype “ Gyrolepis 1” (Gyr1) ( Figure 4 View FIGURE 4 EF): The scale is a rhomboid-shaped piece. The external side is covered by a ganoine layer, ornamented anteroposteriorly by striations that can bifurcate ( Figure 4E View FIGURE 4 ). The ganoine does not cover the anterior margin of the scale. A broad vertical ridge often marks the internal side (Figure 4F).

Scale Morphotype “ Gyrolepis 2” (Gyr2) ( Figure 4 View FIGURE 4 GH): It is more elongated in the anteroposterior direction, showing the shape of a lozenge. The scale is thinner than the first morphotype. The external side has the same ganoine layer with a similar pattern of striations ( Figure 4G View FIGURE 4 ). The internal side does not show any ridge (Figure

4H).

Remarks. The species Gyrolepis albertii Agassiz, 1835 was described from scales from the Muschelkalk (Middle Triassic) of Germany and the Rhaetian of Wickwar ( England) (Agassiz, 1835; Mears et al., 2016). Mears et al. (2016) described five scale morphotypes, including one as G. albertii . In this study, the scales and the teeth described are assigned only to the genus Gyrolepis by following the same reasoning from previous studies: similar lozenge shape, striations that bifurcate, and presence of the anterior margin articulating with the other scales (Allard et al., 2015; Mears et al., 2016; Landon et al., 2017; Cavicchini et al., 2018; Cross et al., 2018; Diependaal and Reumer 2021). De Lange et al. (2023) and this paper noted the absence of ornamentation on some scale morphotypes, probably due to erosion.

Scales with similar morphology to the morphotype Gyr1 have been previously reported (Mears et al., 2016; Cavicchini et al., 2018; Cross et al., 2018), although some were not attributed to G. albertii (e.g., specimen BRSUG 29385 in Landon et al., 2017: figure 6k). Scales with similar morphotypes were later assigned to G. albertii by Diependaal and Reumer (2021). It is difficult to distinguish the smallest teeth of Saurichthys sp. from those of Gyrolepis sp. , as they are not complete and are vertically striated. Only one tooth, specimen NHMD–1811677, correctly matches the morphology of Gyrolepis sp. dentition. Gyrolepis is assigned to the Palaeoniscidae , a wastebasket group typical of the Carboniferous and Permian likely to be paraphyletic (Korneisel et al., 2015). The taxon has a wide stratigraphic range and needs a taxonomic review (Mears et al., 2016). The sharpness of the teeth suggests a carnivorous diet (Moreau et al., 2021). Gyrolepis presence in Europe has been firmly documented (Allard et al., 2015; Mears et al., 2016; Diependaal and Reumer, 2021). It has already been mentioned in Greenland (Clemmensen, 1980b; Jenkins et al., 1994). Another Palaeoniscidae , Glaucolepis artica Stensiö, 1932 , was previously described from the Early Triassic of Greenland, but no teeth have been reported, preventing any comparison with the new specimens.

Actinopterygii indet.

( Figure 4 View FIGURE 4 I-P)

Specimens referred. NHMD–1811680 – ganoid scale; NHMD–1811681 – ganoid scale; NHMD– 1811682 – ganoid scale; NHMD–1811683 – fin ray element; NHMD–1811684 – vertebral centrum; NHMD–1811788 – ganoid scale; NHMD–1811789 – ganoid scale; NHMD–1811790 – ganoid scale; NHMD–1811791 – ganoid scale; NHMD–1811792 – ganoid scale; NHMD–1811793 – ganoid scale; NHMD–1811797 – ganoid scale; NHMD–1811798 – ganoid scale; NHMD–1811799 – ganoid scale; NHMD–1811801 – ganoid scale; NHMD–1811802 – ganoid scale; NHMD–1811803 – ganoid scale; NHMD–1811804 – ganoid scale; NHMD–1811805 – ganoid scale; NHMD–1811806 – ganoid scale; NHMD–1811807 – ganoid scale; NHMD–1811808 – ganoid scale; NHMD–1811809 – vertebral centrum; NHMD–1811810 – vertebral centrum; NHMD–1811811 – vertebral centrum; NHMD– 1811812 – vertebral centrum; NHMD–1811813 – vertebral centrum; NHMD–1811814 – vertebral centrum; NHMD–1811815 – vertebral centrum; NHMD–1811816 – vertebral centrum; NHMD– 1811817 – vertebral centrum; NHMD–1811818 – vertebral centrum; NHMD–1811819 – vertebral centrum; NHMD–1811820 – vertebral centrum. nd 18 additional ganoid scales, and 12 vertebral centrums stored under the collections number NHMD – 1811714. Locality. From site 62/91/G on western side of Tait Bjerg, Jameson Land, East Greenland ( 71°28´34´´ North 22°40´43´´ West). Horizon and age. Thin bone bed in Carlsberg Fjord Member of the Ørsted Dal Formation in the Fleming Fjord Group. Late Triassic (Norian). Description. Various actinopterygians remains, such as scales, fin ray elements, teeth acrodin caps, and vertebral centra. Individual Scales ( Figure 4 View FIGURE 4 I-N): Many fish scales of various shapes that could not be attributed to a specific actinopterygian clade have been gath- GoogleMaps

ered. NHMD–1811680 ( Figure 4 View FIGURE 4 I-J) is vaguely rhomboid with a rounded angle, with the dorsal edge curved and a peg in the anterior extremity.

The external side shows a ganoin layer ornamented by convex sinuous ridges, while the internal side has an oval-shaped convexity.

NHMD–1811681 ( Figure 4 View FIGURE 4 K-L) is a rhomboid that is longer than wider and has a thicker ganoin layer. This layer is smooth with two irregularities: one elongated convexity on the anterior margin and one elongated concavity posteriorly. NHMD–1811682 ( Figure 4 View FIGURE 4 M-N) presents two pegs, one very short and spike-shaped and the second longer and rectangular. Two foramina are visible on the external side, one next to the second peg and the last foramen adjacent to the first peg. On the internal side, a concavity is present and is shaped like the first peg. This structure could have received the peg of the preceding scale.

Fin ray element ( Figure 4O View FIGURE 4 ): It is short, 2 mm long, and composed of two parts. The first one is the bony core, which is circular in cross-section. The second part is the ganoine-covered scale, which is flat. The two parts are connected by bone.

Vertebrae ( Figure 4P View FIGURE 4 ): The vertebral centra are amphicoelic and can be perforated. The base of the haemal arc or the neural arc can be present. Duffin and Gaździcki (1977) described a similar centrum in the Rhaetian of Poland.

Remarks. Site 62/91/G yields unidentified actinopterygian remains, including scales, fin ray elements, teeth acrodin caps, and vertebral centra.

They lack diagnostic features to allow further identification. On top of the two-scale morphotypes previously described, seven other ganoid scale shapes are represented, although no species identification could be made. Based on multiple previous studies, it is approved that ganoid scales are assigned to non-teleost fish (Buscalioni et al.,

2008), with some Teleosteomorpha taxa displaying ganoid scales (Arratia, 2015; Arratia and Schultze,

2024). Thus, every individual ganoid scale not assigned to Gyrolepis sp. is tentatively attributed to non-teleostean Actinopterygii without going further in the identification process.