Candelaria Price, 1947

Müller, Rodrigo T., 2021, An additional specimen of owenettid procolophonoid from the Middle Triassic of Southern Brazil, Acta Palaeontologica Polonica 66 (4), pp. 827-836 : 830-832

Genus Candelaria Price, 1947

Type species: Candelaria barbouri Price, 1947 ; Candelária , Brazil, Ladinian–Carnian, Triassic.

Candelaria barbouri Price, 1947

Fig. 3 .

Holotype: DGM 314 Ra skull and mandible in occlusion ( Price 1947). Type locality: Sanga Pinheiros (29°46′19″ S, 52°44′54″ W), municipality of Candelária , Rio Grande do Sul, Brazil.

Type horizon: Santa Maria Supersequence, Pinheiros-Chiniquá Sequence, Paraná Basin. These strata are Ladinian to early Carnian in age ( Marsicano et al. 2016; Ezcurra et al. 2017; Phillip et al. 2018; Schultz et al. 2020).

Material.— UFSM 11076 and UFSM 11131, two complete skulls with mandibles in occlusion and associated postcrania ( Cisneros et al. 2004). The specimens were excavated from “Cortado” site (29°44′55″S, 53°00′06″W), municipality of Novo Cabrais, Rio Grande do Sul, Brazil ( Da-Rosa et al. 2004). The outcrops pertain to the same horizon as those from which the holotype was recovered ( Cisneros et al. 2004). CAPPA / UFSM 0225, an almost complete skull with mandibles in occlusion. Despite its completeness degree, the bone surface is poorly preserved. The specimen was excavated from from “Posto” site (29°37′35.60″S; 53°22′2.86″W), municipality of Dona Francisca, Rio Grande do Sul, Brazil. This site is Ladinian to early Carnian in age.

Emended diagnosis.—According to Cisneros et al. (2004), Candelaria barbouri differs from all other owenettids by its relatively large size (at least 30% larger than all other known owenettid specimens, but see Bradley and Nesbitt 2017) and by a suite of characters related to the presence of a temporal fenestra.

Description.—Whereas the skull and mandibles are almost completely preserved, bone contacts are poorly discernable ( Fig. 3 ). Furthermore, CAPPA / UFSM 0225 lacks the right portion of the snout. The skull is 43 mm in length. The largest known specimen of Candelaria barbouri is 49 mm in length ( UFSM 11076; Cisneros et al. 2004). Conversely, other owenettids are smaller in size, for instance, the length of the holotypic skull of Ruhuhuaria reiszi Tsuji, Sobral, and Müller, 2013 ( CAMZM M T 997) is 25 mm ( Tsuji et al. 2013). However, an additional specimen ( UMZC T 1162) suggests that R. reiszi could have reached 40 to 50 mm in length ( Bradley and Nesbitt 2017), resembling the size of Candelaria barbouri . The maximum width of the posterior half of the skull is approximately 30 mm. Therefore, the ratio between length and width of the skull is 1.43. In some procolophonids, such as Procolophon trigoniceps Owen, 1876 , and Kapes bentoni Spencer and Storrs, 2002 ( Carroll and Lindsay 1985; Zaher et al. 2019), it is less than 1. The height of the skull with mandibles in occlusion is about the same along its length (anterior half approximately 20.5 mm and posterior half approximately 20 mm). Nevertheless, the specimen shows some degree of dorsoventral sedimentary compression. Whereas the orbits are approximately 15 mm in length, the shape and dimensions of the external nares are uncertain.

Distinct from several parareptiles (e.g., Macroleter poezicus Tverdochlebova and Ivachnenko, 1984 , PIN 4543/3; Nyctiphruretus acudens Efremov, 1938 , PIN 4659/1; Tsuji 2006; Säilä 2010), the specimen lacks ornamentation (i.e., grooves and tubercles) on the dorsal surface of the skull. As typical of procolophonoids, the snout tapers anteriorly and the skull is sub-triangular in dorsal view ( Fig. 3A 1 , A 2 ). The anterior portion of the skull is poorly preserved. Therefore, the number of premaxillary and maxillary teeth, as well as details of the morphology of premaxilla and maxilla are uncertain. The prefrontal forms the anterior and the ventral half of the orbital margin. There is an orbital flange projecting from the anteromedial margin of the orbit ( Fig. 3A 1 , A 2 ), such as in other specimens of C. barbouri (e.g., UFSM 11076, UFSM 11131), where it is formed across the contact between the lacrimal and the prefrontal ( Cisneros et al. 2004). In Owenetta rubidgei Broom, 1939 ( RC 50) and Saurodektes kitchingorum Reisz and Scott, 2002 (BP/1/4195a; Reisz and Scott 2002) it is less developed. The orbit of CAPPA / UFSM 0225 is roofed anteriorly by the prefrontal and frontal, and posteriorly by postfrontal. The latter is large, resembling other owenettids, whereas in procolophonids it is comparatively reduced. Medially, the orbit is rimmed by a longitudinal orbitotemporal crest ( Fig. 3A 1 , A 2 ). This crest is usually present and well-developed in owenetiids ( Cisneros et al. 2004; Tsuji et al. 2013). However, a similar crest occurs in some procolophonids ( Kapes bentoni, BRSUG 29950- 13; Procolophon trigoniceps , CAPPA / UFSM 0189). The frontals are narrow, resulting in a very narrow interorbital breadth, which resembles the condition of Ruhuhuaria reiszi ( CAMZM T 997; Tsuji et al. 2013).

The orbit of CAPPA / UFSM 0225 lacks the posterior enlargement typical of procolophonids. On the other hand, the specimen bears a putative temporal opening, such as Candelaria barbouri ( Cisneros et al. 2004) . The fenestra is located at the dorsal half of the posterior portion of the skull ( Fig. 3A 5 , A 6 ). It is longer (8 mm) than tall (2 mm). The temporal opening is separated from the orbit by the postorbital, which forms the anterior rim of the opening. The postorbital also contributes to the anterior dorsal half of the fenestra, whereas the dorsoventrally short squamosal forms the ventral margin. The lateral margin of the supratemporal bears a notch ( Fig. 3A 1 , A 2 ), which occurs in Saurodektes kitchingorum (BP/1/4195a; BP/1/6025; Reisz and Scott 2002; Modesto et al. 2003) and Owenetta rubidgei ( SAM PK K 7582; Reisz and Scott 2002). This notch is considered absent in the other specimens of C. barbouri ( Cisneros et al. 2004) .

The ventral margin of the posterior portion of the jugal directs dorsally, forming an acute temporal emargination between the contact with the quadratojugal ( Fig. 3A 5 , A 6 ). This contact is reduced and restricted to the posterodorsal corner of the jugal, a typical trait of owenettids ( Reisz and Scott 2002; Modesto et al. 2003). The posterior half of the jugal is dorsoventrally expanded, whereas in Saurodektes kitchingorum (BP/1/4195a) it is slender. The anteroventral corner of the quadratojugal projects anteriorly, forming a sigmoid anterior margin. The quadratojugal lacks any hornlike projection, which is usually present in procolophonines (e.g., Procolophon trigoniceps, NM QR 3201; Teratophon spinigenis Gow, 1977 , SAM PK-K 10174; Cisneros 2008) and leptopleuronines (e.g., Hypsognathus fenneri Gilmore, 1928 , YPM 55831; Sues et al. 2000).

The pineal foramen is small (2 mm in length) and circular in outline. It is located within a depressed surface ( Fig. 3A 1 , A 2 ). Moreover, it rests posterior to posterior margin of the orbit, such as in other owenettids ( Cisneros et al. 2004). In contrast, the posterior margin of the orbitotemporal fenestra of procolophonids is anterior to or at the level of the pineal foramen ( Cisneros 2008). The posterior margin of the skull is straight to concave. It differs the specimen from procolophonids like Pentaedrusaurus ordosianus Li, 1989 ( IVPP V 873) and Mandaphon nadra Tsuji, 2017 ( NMT RB16; Tsuji 2017), which bear a posteriorly projected margin. The posterolateral corner of the skull is rounded and featureless, whereas in Procolophon trigoniceps ( BMNH R 1949; Carroll and Lindsay 1985) the corner forms an acute angle with a prominent spine.

The palate and ventral portion of the braincase are partially visible ( Fig. 3A 3 , A 4 ). The suture between the parasphenoid and basioccipital is obscured. There is a shallow depression on the ventral surface of these bones. The interpterygoid vacuity is long and narrow. The cultriform process is not preserved. The pterygoid is long and wide. On the ventral surface, there is a longitudinal fossa medially bounded by a longitudinal ridge and laterally bounded by an oblique ridge. It resembles the morphology of Saurodektes kitchingorum BP /1/4195a), which bears rudimentary teeth in each ridge. The presence of these teeth in CAPPA / UFSM 0225 is uncertain. The transverse process of the pterygoid is anterolaterally projected. The additional palatal bones are not visible.

The mandible is triangular in ventral view ( Fig. 3A 3 , A 4 ), such as the skull. The posterior portion is far wider than the anterior end. The anterior portion of the mandible shows a gently transverse constriction in ventral view, resulting in a narrow symphyseal region. Conversely, Ruhuhuaria reiszi ( CAMZM T 997) lacks this constriction, showing a parabolic-shaped symphyseal region in ventral view. In lateral view, the dorsoventral height of each mandibular ramus is about the same along its length. Hence, the dorsal and ventral margins of the dentary run parallel. The ventral margin of the anterior end of the dentary is slightly ventrally expanded. The splenial forms the medial surface of the anterior half of the lower jaw. However, its contacts are poorly preserved. The posterior tip of the lower jaw deflects ventrally, whereas in Owenetta rubidgei ( SAM PK K 7582) it is straight. Such as in other owenettids, the craniomandibular articulation occurs approximately at the same dorsoventral level of the dentary tooth line.

Figures

Fig.3. Owenettid procolophonoid Candelaria barbouri (CAPPA/UFSM 0225) from the “Posto” site, Dona Francisca, Rio Grande do Sul, Brazil;Ladinian, Middle Triassic.Skull and mandible in dorsal (A1,A2), ventral (A3.A4), and left lateral (A5,A6) views. Photographs (A1,A3, A5) and explanatory drawings (A2, A4, A6).

Fig. 1. A. Map of the “Posto” site and the surface distribution of the geologic units in the area (modified from Müller et al. 2020). Location of the study area within South America (inset). B. General view of the “Posto” site.

Fig. 2. Reconstructed skeleton of Candelaria barbouri depicting the preserved elements (in brown) of CAPPA/UFSM 0225 (by Maurício S. Garcia).

Fig. 5. Dendrogram from the updated dataset of Martinelli et al. (2017) of main localities of the state of Rio Grande do Sul yielding fossil tetrapods of the Dinodontosaurus Assemblage Zone. The silhouette represents the presence ofCandelaria barbouri.

Fig. 6. Bivariate plot showing the results of the morphospace occupation analysis. Red convex hull corresponds to morphospace of owenettids and blue convex hull corresponds to morphospace of procolophonids.

Fig. 4. Results of the phylogenetic analyses. A. Strict consensus tree of the first analysis depicting the phylogenetic position of CAPPA/UFSM 0225. B. Abbreviated strict consensus tree of the second analysis depicting the phylogenetic position of CAPPA/UFSM 0225. Numbers on nodes represent Bremer support values higher than one and Bootstrap values higher than 50%.