Subphylum Crustacea Brünnich, 1772
Superorder Syncarida Packard, 1895
Order Anaspidacea Calman, 1904
Family Clarkecarididae Brooks, 1962
Genus Clarkecaris Mezzalira, 1952
Clarkecaris brasilicus (Clarke, 1920)
Synonymies
Gampsonyx brasilicus Clarke, 1920, N.Y. State Mus, Bull. 219:137. Est 4, Figs. 9, 10.
Clarkecaris brasilicus (Clarke, 1920) Mezzalira, 1952 Bol. Soc. Bras. Geol. 1(1):48 Est. 3.
Clarkecaris brasilicus (Clarke, 1920) Mezzalira, 1954 Vol. Com. 1° Cent. Paraná: 168.
Clarkecaris brasilicus (Clarke, 1920) Brooks, 1962 Crustaceana 4:229–242.
Clarkecaris brasilicus (Clarke, 1920) Brooks, 1969 Geo. Soc. Am. Part R Arthropoda 4(2) R 358.
Clarkecaris brasilicus (Clarke, 1920) Pinto, 1985 Bol. DNPM (27), 253–259.
Holotype
Gampsonyx brasilicus Clarke, 1920; New York State Museum; number 9738, 9739.
Material Five Clarkecaris
brasilicus specimens GP/1E-5689, GP/1E-5690a, GP/1E-5691, GP/1E-5692, GP/1E-5693.
Localization Rio Claro Municipality, center-east state of São Paulo
Diagnosis (after Pinto 1985): Strong transverse sulcus divides the cephalon in two parts, both presenting two large pterygostomial spines. Eyes pedunculate; second antennae with scaphocerite. Suture between head and first thoracic tergite vestigial: long spinelike thoracic and abdominal pleurae directed anteriorly and posteriorly, respectively, two large supraorbital and two hepatic spines dorsally; furcae present.
Description The complete cephalon is seldom fossilized, so no collected specimens for this study preserved the cephalon entirely. In three of them, only abdominal tergites are reasonably preserved. The species body is narrow and elongate.
Part of the cephalon and impressions of pterygostomial spines are seen in the specimen GP/1E-5691 (Fig. 2a), two of them are laterally disposed. Two small disarticulated thoracic tergites, 0.4 mm long and 4.1 mm wide, containing small spines turned to the frontal part of the fossil.
Only the specimen GP/1E-5692 (Fig. 2c) presents thoracic tergites, which are smooth, with no large ornamentation, almost 1 mm long and 4.1 mm wide, bearing small spines visible on the extremities, turned to the anterior parts of the specimens.
Every specimen, GP/1E-5689 (Fig. 2b), GP/1E-5691 (Fig. 2a), GP/1E-5692 (Fig. 2c) and GP/1E-5693 (Fig. 2d), have the same abdominal tergite features, large rectangular in shape and curved lateral spines, as seen in the specimens GP/1E-5691 and GP/1E-5693. The spines are turned backward on the entire lateral tergite.
The telson is elongate, tapering toward the extremity as seen on the specimens GP/1E-5689, GP/1E-5690a and GP/1E-5693 (Fig. 2b, d, e). The specimen GP/1E-5693 bears uropod remains at one of the flattened sides, turned backward.
The largest figured specimen, GP/1E-5691 is 34 mm long, the body of only 19 mm without the broken up cephalon, and the tergite maximum width is 6 mm. The maximum lateral spine is about 2 mm in size. The lengths of the remaining specimens are 15 mm for GP/1E-5689 (not considered the disarticulated fragment); 16 mm for GP/1E-5692 and 19 mm for GP/1E-5690a.
Discussion The described specimens are typical of the genus Clarkecaris, the preservation of specimens in this silty shales is similar to the preservation of specimens found out elsewhere (Mezzalira 1952).
The holotype, from Guareí Municipality, State of Sao Paulo, was described by Clarke (1920) who considered it a new species of Gampsonyx, on the basis of two fragmented specimens, preserved only the thorax, abdomen and the tail.
Mezzalira (1952) collected better preserved specimens, observing details unavailable before, so he got elements for proposing a new genus, Clarkecaris in the family Uronectidae. Later Brooks (1962) proposed the family Clarkecarididae under the order Anaspidacea, based on fossils in the United States National Museum collection.
Mezzalira (1971) and later Pinto (1985) elaborated detailed descriptions of the pterygostomial spines and cephalic appendices. Only one specimen discovered by Brito and Quadros (1978) and described by Pinto (1985) was not found in the state of São Paulo, coming from State of Paraná, being one of the few complete specimens.
Crustacean occurrences in the Taquaral Member as well as in the Assistência Member were taken by Barbosa and Gomes (1958) as a basis to put them within the Irati Formation. However, Clarkecaris is present only in the Taquaral Member. The Assistência Member crustaceans belong to different taxa. Besides, fossils cannot be taken as criterion for defining lithostratigraphic units. Nevertheless, every Brazilian stratigrapher group together both units in the Irati Formation for the following reasons: (a) no discordance separates them; (b) gradual evolution to a restricted basin is observed as Taquaral passes up to Assistência.
Clarkecaris occurs only in the states of São Paulo and Paraná. It does not occur in Southern Paraná Basin, South Africa, Paraguay, Uruguay and nor in Permian Brazilian basins (Amazonas and Parnaiba Basins).
The paleoenvironment where Clarkecaris lived is an open question, whether salty or fresh water. According to Beurlen (1931), a possible fresh water would be reasonable, because recent Anaspidacea live in freshwater. Mezzalira (1952), in spite of the phylogenetic affinities with Anaspidites, which prefers freshwater, was reticent to admit freshwater. Both Beurlen (1931) and Mezzalira (1952) agreed that a coastal region would be the paleoenvironment which this genus, thus discarding deep waters.
Clarkecaris brasilicus has been compared to Syncaridan (Palaeocaridacea) genera from the Carboniferous of North American as Squillites and Palaeocaris (Brooks, 1962; Schram and Schram, 1974); According to Schram and Schram (1974), Clarkecaris would be an intermediate taxon between the most primitive Palaeocaridacea and the living Anaspidacea.
Squillites was discovered in association with freshwater and euryhaline fossils. Palaeocaris, during long time considered a freshwater genus, was recently mentioned in paleoestuarine environment, with varied salinity (Schultze 2009). The Devonian Syncarida was marine (Schram and Schram 1974) but, in Early Carboniferous, they were adapted to transitional paleoenvironments, brackish and even freshwaters.
Superorder: Indeterminate
Fig. 3
Material One specimen GP/1T-6174.
Localization Rio Claro Municipality, center-east state of São Paulo.
Discussion No pereonite or thoracic somites and other parts of the animals are preserved. The bifurcated structures of the extremities are the main diagnostic feature of this crustacean. The specimen was collected at the same outcrop where Clarkecaris specimens came from.
Foehringer and Langer (2003, 2004) suggested that this taxon would be decapods, Reptantia, based on possible “chelas”. However, Decapoda and Eucarida are rare in the Paleozoic and the few present, are devoid of chelas (Schram and Schram 1974; Schram 1978, 1980, 1981, 2006). The bifurcated structures of the extremities were not used for grabbing objects. Probably they would be a locomotion apparatus, based on the weakness of these articulations. They look like two-tail uropod branches, also present in other Malacostraca (Knopf et al. 2006; Haug et al. 2010; Kutschera et al. 2012). The remains from Taquaral are similar to those of Squillites (Schram and Schram, 1974). However, better preserved fossils will be necessary to get a definition of its taxonomic affinities.
Subphylum Vertebrata Cuvier, 1812
Class Osteichthyes Huxley, 1880
Subclass Actinopterygii Woodward, 1891
Order Indeterminate
Fig. 4
Material Scales (GP/2E-6222a, GP/2E-6222b GP/2E-6223, GP/2E-6225) and one isolated maxilla (GP/2E-6231).
Localization Rio Claro Municipality, center-east state of São Paulo
Description of the scales The scales are well preserved, rhombohedral, as seen from above. Their margins generally are smooth, commonly without the articulatory “peg-and-socket” system, although it is clearly seen in some specimens (Fig. 4a–d) sometimes standing out as a projected off point at one side of the scale (Fig. 4c). Sometimes this system is weakly distinguished at one side (Fig. 4a, b, d).
Description of the maxilla Only one bone makes up the maxilla, with two distinguished parts: one frontal suborbital, below the ocular region and the other posterior to the orbit, behind the ocular region. Suborbital is narrow, gradually thinning on the frontal face, with the posterior ventral region elongate, projected forward, from the articulation with the lower jaw. The postorbital region is 16.7 mm long and 2.9 mm high. The thinner region of suborbital is practically straight, without any curves, high and elongate, 7.9 mm long, with small teeth along the inferior face.
The poor preservation does not allow the observation of possible features like ornamentations or irregularities on the surface.
The conical teeth are very small but strong, their lengths are smaller than 1 mm, commoner on the internal face, near this postorbital.
Discussion Richter et al. (1985) proposed informal morphological classification (P1–P5 morphotypes) for the Parana Basin, Late Paleozoic, paleoniscoid scales. The Taquaral Member silty shale facies bears two types of smooth scales (P1 and P5) and only one ornamented scale (P3).
Besides the rhombohedrical scales, few angular scales may be associated with several dermic bones and fulcral scales. These bones and scales are similar to those associated with northern hemisphere Elonichthys, interpreted by Schultze and Bardack (1987) as belonging to fins of this genus.
Unfortunately only one maxilla was found in the Taquaral silty shale facies. Its pattern is typical of Paleoniscoid maxilla. The elongate shape of the postorbital is observed in older forms, like the North American Carboniferous Paratarrasius (Lund and Poplin, 2002), as well as in younger forms, like Brasilichthyes (Cox and Hutchinson, 1991), from the northern Brazil Permian Pedra do Fogo Formation, Parnaiba Basin.
Several genera bearing jaws were described from the Permian Parana Basin formations, as from the Rio do Sul formation, which is older than the Irati Formation, bears the genus Roslerichthys, described by Hamel (2005). From the Corumbataí Formation, younger than Irati, three genera were described: Tholonotus (Dunkle and Schaeffer, 1956), Angatubichthys (Figueiredo and Carvalho, 2004) and Santosichthys (Figueiredo and Gallo, 2006a, b).
The postorbital maxillas of these genera are not so elongate as the presently described. Possibly the maxilla, described here, belongs to a new taxon.
The narrow suborbital and elongate postorbital maxilla of the North American Carboniferous genus Wendyichthys (Lund and Poplin, 1997) are similar to those of the Taquaral maxilla, but the lack of other Taquaral fossils prevents a closer comparison with this genus.
Subclass Sarcopterygii Romer, 1955
Infraclass Actinistia Cope, 1871
Order Coelacanthiformes Berg, 1937
Family Indeterminate
Material Isolated scales part and counterpart: GP/2E-5969a and b; GP/2E-6233a and b.
Localization Rio Claro Municipality, center-east state of São Paulo.
Description The scales, part and counterpart are well preserved, revealing details of their anatomy. The imbrication region is marked by several longitudinal short and thick ribs, sometimes overlying each other but not ramifying (Fig. 5a–e). The ribs are smooth, shaping as small irregular cylindrical tubes of different sizes.
The growth lines, near the imbrication zone, are joined and slightly curved. However, lines represent growing, thus they acquire different orientations.
The scale GP/2E-5969 (Fig. 5a–b) is 6.8 mm long, 6.2 mm wide and 0.1 mm thick. The distal part is 4.5 mm long. The imbrication zone is around 2.3 mm long. The width of the articulatory region is smaller than the maximum width of the scale (4.0 mm).
The specimen GP/2E-6233 (Fig. 5c, d) is larger, 12 mm long and 12.8 mm wide. The thickness does not exceed 0.1 mm. The preservation of the distal part is incomplete, so with different lengths, however, it was possible to measure the imbrication zone length, which is approximately 8.5 m. The articulatory region is 10 mm long.
Discussion The described scales are very similar to those of the living Indian Ocean Coelacanthidae (Latimeria) so they are placed in the Coelacanthiformes.
The shapes of the growth lines and articulatory zone of the Taquaral scales are very similar to those from the State of Sao Paulo late Carboniferous Itararé Subgroup (Bryant 1929) as well as from the State of Rio Grande do Sul, early Permian of the same Subgroup (Barcellos 1975). Also the scale identified by Richter (1985), from the Irati Formation of Rio Grande do Sul and the scales from state of São Paulo Corumbataí Formation, have similar imbrication zones.
Scales of Coelacanthiformes are rarely found out in beds of the Permian Tatuí Formation, State of Sao Paulo, located under the Taquaral Member, as well as, in the basal sandy facies of the Taquaral Member (Chahud and Petri 2009). They are otherwise, rather common in the silty shale facies of the Taquaral Member, frequently associated with the crustacean Clarkecaris and with remains of Palaeonisciformes. These differences of fossil contents probably would be responses from different conditions of preservation.