Albanerpeton pannonicum Venczel & Gardner, 2005
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publication ID |
https://doi.org/ 10.5252/geodiversitas2021v43a14 |
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publication LSID |
urn:lsid:zoobank.org:pub:5EDF5351-1F3B-43A7-B88C-C72E2A511176 |
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DOI |
https://doi.org/10.5281/zenodo.5076266 |
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persistent identifier |
https://treatment.plazi.org/id/BD27293F-FFD5-FF85-FF21-FB10FED3FDA8 |
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treatment provided by |
Felipe |
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scientific name |
Albanerpeton pannonicum Venczel & Gardner, 2005 |
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Albanerpeton pannonicum Venczel & Gardner, 2005 ( Figs 3 View FIG ; 4 View FIG )
MATERIAL. — Fifty-five isolated bones: Italy. MoncuccoTorinese, Layer M3 (n = 3): Premaxilla (n = 1): MGPT-PU 132112. Dentaries (n = 2): MGPT-PU 132630, 132631. — Layer M3/4 (n = 10): Maxilla (n = 1): MGPT-PU 132274. Dentaries (n = 9): MGPT-PU 132640-132647, 132652. — Layer M4 (n = 1): Sacral vertebra (n = 1): MGPT-PU 132017 .— Layer M4/5(n = 20): Premaxillae(n = 3): MGPT-PU 132001, 132002, 132232.Maxillae (n = 4): MGPT-PU 132011, 132012, 132632, 132633.Dentaries (n= 11): MGPT-PU132005-132009,132634-132639. Trunk vertebrae (n = 2): MGPT-PU 132015, 132016 . — Layer M5 (n = 2): Dentaries (n = 2): MGPT-PU 132003, 132004 . — Layer M7+25 (n = 6): Premaxillae (n = 4): MGPT-PU 132648-132651.Dentaries (n = 2): MGPT-PU 132653, 132654.
Collected in situ, from unrecorded layer(s) (n = 4): Premaxilla (n = 1): MGPT-PU 132165. Maxilla (n = 1): MGPT-PU 132307. Dentaries (n = 2): MGPT-PU 132318, 132319.
Surface collected, from unknown layer(s) (n = 9): Maxillae (n = 2): MGPT-PU 132013, 132014. Dentaries (n = 7): MGPT-PU 132010, 132655-132660.
DESCRIPTION OF MONCUCCO TORINESE ALBANERPETONTID SPECIMENS
Premaxillae ( Fig. 3 View FIG A-L)
Nine isolated premaxillae are available. The best-preserved specimen is MGPT-PU 132112 ( Fig. 3 View FIG A-C), an intact left
premaxilla. Most other specimens (e.g., Fig. 3 View FIG D-L) preserve an intact dorsally directed pars dorsalis, at least some portion of the lingually directed pars palatinum, and much of the ventrally directed pars dentalis and its tooth row. All premaxillae are relatively small (total intact heights range from 1.5-1.7 mm), yet are comparatively robust in build when compared to similar sized premaxillae of other albanerpetontids (e.g., Gardner 1999b: text-fig. 2A-E). The medial edge is straight and bears prominent, vertical grooves and flanges for strong sutural contact or, perhaps, weak fusion (although no examples of fused premaxillae are present in our sample) in life between the paired premaxillae. In the eight specimens preserving an intact pars dorsalis, the process is moderately tall and broad, with the ratio of maximum height vs width across the suprapalatal pit ranging from 1.30-1.55 (i.e., relative height is “low” sensu Gardner 2002; Venczel & Gardner 2005). The dorsal edge of the pars dorsalis is slightly swollen labiolingually and is roughened for abutting or weak sutural contact with the nasal. As seen in the five figured premaxillae, considerable variation is evident in the outline of the dorsal end of the pars dorsalis, the relative depth and width of the lateral dorsal notch along the upper portion of the pars dorsalis, and the outline of the laterally directed swelling immediately below the lateral dorsal notch ( Fig. 3A, D, G, I, K View FIG ). The uppermost portion of the pars dorsalis labially bears a low bony boss that is weakly ornamented with irregular-shaped, small pits and low ridges. The remainder of the premaxillary labial surface is relatively smooth, aside from small and scattered nutritive foramina. Midway across its lower half, the lingual surface of the pars dorsalis bears a suprapalatal pit that faces lingually, is moderately large and undivided, has an asymmetrically ovoid to subtriangular outline, and is bounded laterally by an obliquely oriented bony strut ( Fig. 3C, F, H, J, L View FIG ). Preserved intact on just one specimen, MGPT-PU 132112 ( Fig. 3B, C View FIG ), the pars palatinum is a shallow, bony shelf that medially bears a lingually projecting, triangular vomerine process and laterally is expanded into a maxillary process for contact with the maxilla. The central portion of the pars palatinum is pierced by a prominent palatal foramen that opens into the floor of the suprapalatal pit. The palatal foramen is subcircular and varies in size, with its diameter ranging from approximately the same as the diameter of shafts of medial teeth on the same specimen to twice the diameter of those shafts. The pars dentalis is relatively deep. Five premaxillae preserve an intact tooth row, consisting of either seven or eight tooth positions (two and three specimens, respectively). Teeth are typical for albanerpetontids in being highly pleurodont, non-pedicellate, and closely spaced in a comb-like arrangement, in having shafts that are deep, straight, cylindrical, and slightly mesiodistally compressed, and in bearing chisel-shaped crowns that are labiolingually compressed and mesiodistally tricuspid, with the median cusp most prominent. Some premaxillae have fully functional teeth occupying all loci (e.g., Fig. 3C, J View FIG ), whereas others have one or several empty tooth slots (e.g., Fig. 3F View FIG ). One of the figured examples ( Fig. 3L View FIG ) exhibits a nearly functional replacement tooth in its fifth locus from the mesial (= medial) end.
Maxillae ( Fig. 3 View FIG M-S)
The most nearly complete and informative of the eight maxillary specimens is MGPT-PU 132307 ( Fig. 3 View FIG M-O), a right maxilla missing only a small piece from the anteroventral portion of its premaxillary lateral process and the distal ends of five teeth. Considering the minor amount of breakage at its anterior end, the specimen’s preserved
maximum length of 2.7 mm likely reflects the true size of that maxilla. Although the other two figured specimens are less nearly complete, when intact those maxillae would have been slightly smaller (MGPT-PU 132012: Fig. 3P, Q View FIG ) and larger (MGPT-PU 132014: Fig. 3R, S View FIG ) in their maximum lengths compared to MGPT-PU 132307. As best shown by MGPT-PU 132307 and, to a lesser extent by MGPT-PU
132012, in overall form the maxilla is moderately elongate, low, and triangular in labial or lingual outline. The pars dorsalis increases in height anteriorly, culminating in the dorsally projecting, triangular nasal process having a leading edge that is either nearly vertical or shallowly concave in labial or lingual outline (cf., Fig. 3M View FIG vs Fig. 3P, R View FIG ). The pars dorsalis extends forward below and past the level of the nasal process as a moderately elongate premaxillary lateral process that, in life, labially (= laterally) overlapped with a corresponding facet on the premaxilla (see Venczel & Gardner 2005: text-fig. 1A). The intact premaxillary lateral process preserved on MGPT-PU 132014 ( Fig. 3R, S View FIG ) is bluntly pointed in labial or lingual outline. From the posterior base of the nasal process backwards to the posterior end of the bone, the dorsal surface of the pars facialis is slightly flattened where, in life, it was overlain by the jugal and lacrimal (see Venczel & Gardner 2005: text-fig. 4). The labial surface of the maxilla is smooth, aside from a few small external nutritive foramina arranged in a loose row along about the anterior one-half of the bone. The lingual surface of the maxilla bears a lingually directed, shelf-like pars palatinum that is broadest anteriorly and narrows posteriorly ( Fig. 3O View FIG ). The anterior end of the pars palatinum is expanded into the premaxillary dorsal process that, in life, dorsally overlapped onto the similarly expanded lateral portion (= maxillary process) of the pars palatinum on the premaxilla. More posteriorly, the medial edge of the pars palatinum is indented by a shallow concavity forming the lateral margin of the internal narial opening and the dorsal surface of the shelf bears short ridges and a trough for contact, in life, with palatal bones. The pars dentalis is deepest anteriorly, becomes shallower posteriorly, and its ventral margin is essentially straight in labial or lingual outline. Starting at a point approximately below the leading edge of the nasal process ( Fig. 3N, S View FIG ), the maxillary tooth row extends backwards to the posterior end of the bone ( Fig. 3N View FIG ). The only maxilla with an intact tooth row, MGPT-PU 132307 ( Fig. 3N View FIG ), has 19 tooth positions comprised of 13 intact teeth, five broken tooth shafts, and one empty tooth slot. Teeth are similar in form, attachment, and arrangement to the premaxillary teeth. Maxillary teeth are weakly heterodont in size, being longest about one-third of the distance along the tooth row. MGPT-PU 132012 ( Fig. 3Q View FIG ) preserves a misshaped, slightly procurved replacement tooth in the fifth preserved locus from the mesial (= anterior) end, whereas MGPT-PU 132014 ( Fig. 3S View FIG ) preserves a similarly misshaped functional tooth in the second locus from the mesial end.
Dentaries ( Fig. 4 View FIG A-M)
None of the 35 dentaries is complete, but collectively they document much of the structure of this element. The most nearly complete specimen is MGPT-PU 132003 ( Fig. 4 View FIG A-C), a right dentary preserving about the anterior four-fifths of the bone, including the entire tooth-bearing region and the anterior part of the area for attachment of the post-dentary bones. As best shown by MGPT-PU 132003, the dentary is elongate and moderately deep along its length in labial
or lingual view, and is broadly curved in dorsal or ventral view. In labial view ( Fig. 4A, D, G, J, L View FIG ), the dorsal edge of the tooth-bearing region is essentially horizontal. Behind the tooth row, the dorsal edge bears a low, almost indistinct, dorsally directed swelling and, more posteriorly, the dorsal edge descends shallowly above the area for attachment of the post-dentary bones. The labial surface of the bone is unornamented, although it is slightly roughened and, along the tooth-bearing portion, is perforated by a half dozen or more, moderate sized external nutritive foramina loosely arranged in either one or two horizontal rows (cf., Fig. 4G View FIG vs Fig. 4A, D View FIG ). As seen in lingual and dorsal views ( Fig. 4B, E, H and C, F. I View FIG , respectively), the symphyseal end of the dentary consists of an anteriorly swollen, flat, vertical face and, more posteriorly, bears either one or two short, medioposteriorly directed prongs that, in life, formed a mortise-in-tenon style inter-symphyseal joint. The toothbearing portion consists of a relatively tall dental parapet that becomes shallower posteriorly and a well-developed subdental shelf with a gutter-like dorsal surface. The subdental shelf becomes narrower and deeper posteriorly. Near the end of the tooth row, the subdental shelf is perforated by the large posterior opening for the Meckelian canal and, more posteriorly, in the area lingually (= medially) overlain in life by the post-dentary bones (see Venczel & Gardner 2005: text-fig. 5A, D), the lingual surface of the dentary is shallowly concave and bears thin, posteriorly extending bony ridges. The few specimens preserving a complete or nearly complete tooth row (e.g., MGPT-PU 132003: Fig. 4 View FIG A-C) indicate that 20-25 tooth positions were present. Teeth are similar in form, attachment, and arrangement to those on the upper jaws and, like on the maxilla, dentary teeth are weakly heterodont in size, with the longest teeth occurring about one-third of the distance along the tooth row. The anterior portion of a right dentary, MGPT-PU 132010 ( Fig. 4G, H View FIG ), is notable for having an anomalous, plate-like patch of bone developed on the underside of its symphyseal region.
Vertebrae ( Fig. 4 View FIG N-U)
Although incomplete and less distinctive than the abovedescribed jaws, albanerpetontid post-atlantal vertebrae can be recognized by a suite of features ( Estes & Hoffstetter 1976; Estes 1981; McGowan 1996; Wiechmann 2003; Venczel & Gardner 2005; Sweetman & Gardner 2013; Matsumoto & Evans 2018), including: small size; centra amphicoelous, notochordal, external surfaces relatively smooth, and bearing donut-like ring of calcification around cotylar rims; no spinal foramina; and unicipital rib-bearers. Two trunk vertebrae and one sacral vertebra are available from Moncucco Torinese; here we figure the better preserved trunk vertebra (MGPT-PU 132015: Fig. 4 View FIG N-P) and the sole sacral vertebra (MGPT-PU 132017: Fig. 4 View FIG Q-U). All three specimens are tiny (maximum centra lengths = 1.2-1.4 mm). Each consists of an intact centrum, the broken bases of the neural arch walls, and varying amounts of the transverse processes. Judging from the broken bases of the neural arch walls, the neural arches and
rcc
canals were broad. In each specimen, the centrum is deeply amphicoelous and perforated by a persistent or open notochord, the anterior and posterior cotyles are rimmed with a donut-like ring of calcified cartilage, and no spinal foramina or ventromedian keel are present. In both trunk vertebrae, the centrum is relatively elongate and somewhat hourglass-shaped (i.e., moderately constricted midway along its length), the anterior and posterior cotyles are subcircular in outline, and a faint ridge extends posteriorly and slightly laterally along either side of the ventral midline. On both trunk vertebrae, the broken bases of the transverse processes are positioned low on the broken neural arch wall, slightly forward of the anteroposterior midpoint of the centrum. Judging by their broken bases, the transverse processes were rod-shaped. Trunk vertebra MGPT-PU 132015 bears weakly-developed anterior basapophyses in the form of low, anteroposteriorly short knobs that barely extend forward beyond the anterior cotylar rim ( Fig. 4 View FIG N-P); the other trunk vertebra (MGPT- PU 132016: unfigured) lacks anterior basapophyses. We identify MGPT-PU 132017 ( Fig. 4 View FIG Q-U) as a sacral vertebra because its centrum is relatively broad and anteroposteriorly short, not constricted, and slightly flattened dorsoventrally, it lacks basapophyses, and it bears deep and stout transverse processes that arise lower on the neural arch wall. Although the form of the transverse processes on MGPT-PU 132017 resembles those on anteriormost trunk vertebrae figured by Estes & Hoffstetter (1976: fig. 2A, B, pl. VI, 12, 13) for Albanerpeton inexpectatum , the latter specimens differ from MGPT-PU 132017 in bearing both anterior and posterior basapophyses.
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