Uncinatograptus lisandroi, Lopez & Conde & Braeckman & Segura & Drovandi & Bueno & Abarca, 2024

Uncinatograptus lisandroi sp. nov.

Figs. 4G–J View Fig , 5A–E View Fig , 6A View Fig .

Zoobank LSID: urn:lsid:zoobank.org:act:09E7BF7D-D620-457B-B6BA-824DDEEAB8CA

Etymology: In honour of Lisandro Lopez Gordillo (born 2022), son of FEL, a lovely little boy that gives love and kindness to everyone, and who nowadays inspires FEL to continue his research.

Type material: Holotype: INGEO-PI-2134A, mature well preserved tubarium. Paratypes: INGEO-PI-2134B, countermould of holotype; INGEO-PI-2040, 2062, 2092, mature specimens with moderate preservation; INGEO-PI-2046A, 2048A, juvenile specimens. All from the type locality and horizon.

Type locality: Poblete Norte Creek , Talacasto, 77 km NNW from San Juan city. Central Precordillera , San Juan, Argentina .

Type horizon: PNN-02N, North detailed section, Middle Member of the Los Espejos Formation, Poblete Norte section, Talacasto, lower Gorstian, lower Ludlow, Silurian.

Material.—13 proximal ends or complete specimens in relief (INGEO-PI-2023, 2029, 2040, 2042, 2044, 2046A–C, 2048A, B, 2083, 2092, 2093, 2108A–C, 2126, 2133A, B, 2134A, B, 2137A, B) filled by carbonate or oxidized pyrite. Levels PNN-02N, 06S, and 06’S, all from the type locality and horizon.

Diagnosis.—Slightly to moderately dorsally curved Uncinatograptus , with generally slender tubarium. Sicula and first theca gently to moderately ventrally curved. Dorso-ventral width of 0.52 mm proximally, 0.71 mm medially, and 0.51 mm distally, giving a parallel-sided shape to the tubarium. Hoods rarely preserved. Thecae number 5–8 in 5 mm, 2TRD is 1.38 mm proximally and 1.74 mm distally, interthecal septum inclination decreases from 32–40° proximally to 28° distally.

Description.—Specimens with slightly to moderately proximal ventral curvature, gently to moderately dorsally curved in the middle and distal part. The maximum length is 10.99 mm (INGEO-PI-2092). The dorso-ventral width varies from 0.49–0.69 mm (0.52 mm mean value) at Th1, 0.52– 0.78 mm (0.62 mm) at Th2, 0.49–0.78 mm (0.64 mm) at Th3, 0.60–0.79 mm (0.71 mm) at Th5, 0.63–0.78 mm (0.73 mm) at Th7, 0.61–0.62 mm (0.61 mm) at Th10, and 0.45–0.70 mm 0.51 mm) distally. Sicula is moderately to strongly ventrally curved, 1.89–2.21 mm long, and its apex reaches up to the level of the Th2 aperture. Sicular aperture is 0.23–0.40 mm wide. Downwardly to slightly ventrally-directed virgella 0.14–0.75 mm long, commonly having 0.05–0.14 mm long dorsal tongue. The distance between the sicular and the Th1 apertures varies from 1.18–1.65 mm (1.28 mm mean value). Thecae of uncinatograptid-type finished with hoods and extroverted ventrally facing apertures. Due to taphonomic reasons these hoods are usually not visible or seen in cross section, giving the aspect a pseudomonoclimacid appearance or apertural spines. The supragenicular ventral walls are parallel or inclined slightly inwards to the tubarium axis. Interthecae septum inclines at 32–40° proximally, decreasing to 28° distally. The 2TRD values range from 1.38 mm proximally to 1.74 mm distally. Thecae number 5–8 in 5 mm, and overlap for mostly half their length.

Remarks.—Common components of the lower and middle graptolitic levels of the Los Espejos Formation in different astogenetic stages. Specimens of U. lisandroi sp. nov. can be differentiated from other Uncinatograptus species by its dorso-ventral width, which starts 0.49–0.69 mm at Th1, and from Th2 maintains constant values measured in the respective specimens (minimums of 0.45–0.52 mm to maximums of 0.62–0.79 mm). This width development differs from the constant growth of U. u. uncinatus and U. u. notouncinatus, and the half spindle-shape of U. elsae sp. nov. Furthermore, proximal interthecal septum inclinations are smaller than those showed by U. u. uncinatus (54°), and distal interthecal septum inclination and distal 2TRD show lower values than U. u. notouncinatus (40° and 1.97 mm) and U. elsae sp. nov. (48–56° and 1.86 mm). These minute differences are summarized in Fig. 6 View Fig . On the other hand, if the tubarium presents only proximal features or belongs to a juvenile astogenetic stage, a taxonomic classification at species level will be imposible.

Stratigraphic and geographic range.—Levels PNN-02N, 06S, and 06’S, middle to upper Los Espejos Formation, lower Gorstian, lower Ludlow, upper Silurian. Poblete Norte section, Talacasto area, San Juan Province, Argentina.

Uncinatograptus uncinatus notouncinatus ( Cuerda, 1969)

Figs. 4A–C View Fig , 6B View Fig .

1969 Monograptus uncinatus notouncinatus ; Cuerda 1969: 228–231, pl. 1e–h; pl. 2: 1–3.

1971 Monograptus uncinatus notouncinatus Cuerda, 1969 ; Cuerda 1971: 396–399, pl. 5: 12–23; pl. 31: 1–3.

1975 Monograptus uncinatus notouncinatus Cuerda, 1969 ; Antonioli 1975: 212–216, pl. 1a–k; pl. 2: 1–2.

1996 Monograptus uncinatus notouncinatus Cuerda, 1969 ; Rickards et al. 1996: 114–115, figs. 6j–l, 11c–g.

2019 Monograptus uncinatus var. notounciantus Cuerda, 1969 ; Lopez 2019: 75–77, figs. 21a–g, j, 22a.

Material.—Several juvenile and mature tubaria (INGEO-PI-1863, 1868, 2016A, B, 2023, 2025, 2032, 2044, 2062, 2067, 2074, 2077, 2093, 2101, 2103A, B–2104A, B, 2109A–C, 2115, 2123, 2126–2127A, B, 2134A, B, 2152, 2156, 2173A, B, 2193, 2197, 2209, 2229A, B, 2235, 2238–2246) well preserved as carbon films or filled by carbonate siltstone, from levels PNN-00N–03N, 02S, 04S, 06S, and 06’S, middle to upper Los Espejos Formation, lower Gorstian, lower Ludlow, upper Silurian. Poblete Norte section, Talacasto area, San Juan Province of Argentina.

Description.—The specimens are abundant in the Los Espejos Formation and represented by both juvenile and mature tubaria. Generally, they are preserved in relief, filled by carbonate or oxidized pyrite, as carbon films or negative casts. The analysed material exhibits a straight to slightly dorsally curved tubarium, with a ventrally curved proximal end. The longest specimen with 14 thecae attained the length of 14.5 mm. The dorso-ventral width, thecal spacing, and 2TRD measures are summarized in the Fig. 6 View Fig . Thecae are extroverted throughout the tubarium, although most have lost the hood as a result of preservation and simulate a hoodlike aperture or the presence of spines. The supragenicular walls are parallel or inclined with obtuse angles to the tubarium axis. The sicula is 1.75–2.32 mm long, presents an aperture of 0.28–0.36 mm long, its apex reaches the Th2 aperture, and possesses from two to seven sicular annuli. The thecal overlap is one half. The interthecal septum tilting varies from 40° proximally to 30–27° distally.

Remarks.—These features agree with those given by Cuerda (1969), Antonioli (1975), and Rickards et al. (1996) for U. u. notouncinatus. It is important noting that the dorso-ventral width continuously increase from the proximal (0.62 mm) to the distal area (0.99 mm), in contrast to U. elsae sp. nov. and U. lisandroi sp. nov. ( Fig. 6 View Fig ).

Stratigraphic and geographic range.—Levels PNN-00N– 03N, 02S, 04S, 06S, and 06’S, middle to upper Los Espejos Formation, lower Gorstian, lower Ludlow, upper Silurian. Poblete Norte section, Talacasto area, San Juan Province of Argentina.