of Cretaceous dipnoans from Argentina ( Sarcopterygii : Dipnoi ) with descriptions of new species

In this paper we review the fossil ceratodontiform record from the Cretaceous of Argentina. We report the oldest dipnoan record from Argentina, coming from the Cenomanian of Northwestern Patagonia, Río Negro province. The species «†Ceratodus» iheringi is reassigned. Additionally, four new species are described. Ceratodontiforms were considered extinct in Laurasia after the mid-Cretaceous, with a brief «reappearance» during the Maastrichtian before their definitive extinction from South America and most of the world by K/P bound-ary. Based on our phylogenetic analysis, using characters derived primarily from tooth plates, we propose that the genus †Metaceratodus is more closely related to Neoceratodus than either is to †Ceratodus or †Ptychoceratodus, supporting prior hypotheses. In two most parsimonious trees, the two new genera here described are basal, being one of them sister taxa to Ceratodontoidea nov. and the other unresolved with respect to Protopterus.

Dipnoi (lungfishes) are a monophyletic group of sarcopterygians, restricted today to the Southern Hemisphere (Kemp, 1997).They are represented by two living orders: Lepidosireniformes (Africa and South America) and Ceratodontiformes (Australia).During the Paleozoic and Mesozoic, however, dipnoans had a global distribution.In South America, the record of ceratodontiforms spans the Late Cenomanian (Apesteguía et al ., 2001) through the Paleocene (Schultze, 1991).In Argentina, ceratodontiforms are perhaps the most abundant fossils found in formations representing the 'Lacustrine Senonian', the first stages of the Campanian-Maastrichtian sea transgression (e.g.Los Alamitos, La Colonia, Paso del Sapo Formations; Pascual & ondesio, 1976).B Since Ameghino (1899) described the tooth plate of ´ †Ceratodus´ iheringi, from the Mata Amarilla Formation (see F. Ameghino, 1906 andC. Ameghino, 1916), their systematic position remained uncertain (Martin, 1981(Martin, , 1982)).Despite the fact that in Argentina, localities yield an abundance of fossil dipnoan tooth plates (Fig. 1a), the diver-sity and stratigraphic distribution of these speci-mens has not been reported throughly.This is also true for the remaining countries of South America, where the Cretaceous record of dipnoans is sparse and strongly biased (Souza Cunha & Ferreira, 1980;Gayet & Brito, 1989;Schultze, 1991).
Few phylogenetic reviews have been conducted on fossil dipnoans from Argentina due to the lack of morphological data beyond tooth plates.Martin (1982: p. 56) reviewed the ceratodontiform record of Argentina as part of an analysis of postpaleozoic lungfishes, and from the Campanian-Maastrichtian of the Los Alamitos Formation.Cione (1987) described ' †Ceratodus' iheringi. Both Martin (1982) and ione (1987) related ' †Ceratodus' iheringi with C †Ptychoceratodus madagascarensis.Kemp (1997) reassigned ' †Ceratodus' iheringi to †Metaceratodus, whereas Schultze (1991) (see also Kirkland, 1987) proposed that they were related to those coming from the Upper Jurassic of North merica and the Upper Cretaceous of Madagascar.A In this paper we conduct a new study of Argentinian ceratodontiform systematics, promp-ted by the discovery of well-preserved ceratodontiform tooth plates from several Cretaceous beds of Patagonia.We also address the value of tooth plates in systematic analyses and review the temporal distribution of South American Ceratodontiformes.

METHODS
Our character matrix includes characters adapted from Martin (1982), Martin et al. (1999), Kirkland (1988), and Kemp (1998), as well as new characters discovered and scored for this study (see Appendix 1).Parsimony analysis was performed on the matrix of 9 taxa and 28 characters (see Appendix 2).Ceratodontiform tooth plates examined are primarily Jurassic and post-Jurassic, with one exception, the Triassic †ceratodontid †Ptychoceratodus (Jaeckel 1926) due to its relevance to Gondwanan taxa.The matrix was analyzed with NONA (Goloboff, 1993).The analysis resulted in two most parsi-monious trees, the strict consensus of which re-sulted in a single tree (Fig. 6).( Diagnosis.Small sized (see Table I).All the ridge crests of tooth plates are acute and gracile.Upper tooth plates have five ridge crests and the lower have four.The first upper ridge crest is curved and the others are nearly straight.The last two upper ridge crests are rather similar in size nd oriented strongly backwards.a Etymology.Ameghino, for Florentino, Carlos and Juan, the formidable team of brothers that strenghtened the Paleontological bases in Argentina.†Ameghinoceratodus iheringi (Ameghino, 1899) nov.comb.(Fig. 2 C -E) Diagnosis.As for the genus.Holotype.MLP 1-967, left upper tooth plate (Fig. 2C). 2 Referred material.Materials recently collected in the Mata Amarilla Formation (Goin et al., 2002, and pers. obs Comments.†Ameghinoceratodus iheringi, consigned by Ameghino as Ceratodus iheringi, has an exceptionally wide biochron that extends from Cenomanian to Maastrichtian times.We did not include †Ameghinoceratodus iheringi nov.within the genera †Metaceratodus or †Ptychoceratodus (contra Kemp, 1997;Martin, 1982) because it lacks several derived characters shared by the aforementioned genera, such as: medial edge of lower tooth plates not bent and lingual margin of tooth plates straight or concave (instead of convex).The material MCF-PVPH-572 from the Portezuelo Formation (Fig. 5g) can be assigned to this genus because of the strongly backwards oriented last two upper ridge crests, that are also similar in size each other.

ri
Remarks.†Ceratodontidae (sensu Gill, 1872) refers to the type species †Ceratodus latissimus (Agassiz, 1838), and for diagnosis of the subfamily †Ceratodontinae.Taking into account the almost identical morphology of †Ceratodus sturii respect to C. latissimus (Fig. 2j) and the presence of highly diagnostic cranial materials, we have used †Ceratodus sturii (Teller, 1891) as the represen-tative of the genus in our phylogenetic analysis (Fig. 6).†Ceratodontinae (Gill, 1872)  Modified definition.Ceratodontiform dipnoans more closely related to †Ceratodus sturii than to †Ptychoceratodus serratus.The taxon was evaluated only for species of Ceratodus but fur-ther phylogenetic analyses could show other en-era as included here.
Type species.†Ceratodus latissimus Agassiz, 838 (Fig. 2j) 1 Definition.The node that includes Neoceratodontidae, †Ceratodontidae ( †Ptychoceratodontinae + †Ceratodontinae), their common ancestor and all of its descendants. g Diagnosis.Tooth plates with low and wide ridge crests.Martin, 1982) in having a reduced fifth ridge crest and a tall third crest ridge.It is similar to †C. fossanovum (Kirkland, 1988)  Horizon and locality.Bajo de la Carpa Formation (Santonian).Paso Córdova (Río Negro rovince).P Description.The tooth plate is subtriangular, with four robust and short crests.Clefts between the ridges are wide and shallow.The labial profile of the crests is not steep and ends in a single last crest.The crests are nearly straight.The first crest is long and broad, more pronounced than the adjacent two crests, without a marked slope and only slightly bent, preserving a rostral instead of a lateral direction.The ABC angle is pronounced as in Ameghino-ceratodus rather than gentle as in Ptycho-ceratodus.The fourth crest is very wide, square and its occlusal surface is nearly flat.Caudally and lingually from the fourth crest, there is a marked depression for an upper crest.Occlusal pits are nearly absent in the occlusal surface.The second and third crests are orsally convex.d †Ceratodus kaopen is similar to †C. frazieri, (Ostrom, 1970) from the Jurassic Morrison Formation (United States) in having a large first ridge crest, and in showing an anteroposteriorly expanded fourth ridge crest forming a flat crushing surface (Kirkland, 1987).

Other ceratodontids
By 1995 to 1999, Rodolfo Coria's parties to the Bayo Mesa, Cerros Colorados and Portezuelo Hills collected abundant material of cerato-dontiform dipnoans.They were briefly mentioned in an abstract (Coria et al., 1996) and kindly of-fered to be studied here.These specimens are important as they are stratigraphically far from any marine transgression and they clearly sup-port the abundance and big size of dipnoans in fluvial and l custrine fully freshwater environ-ments.a Recorded ceratodontids include the material MCF- 432,500 (Figs. 4a,c,e), belonging to the genus Ceratodus itself, considering their rounded crests, with a low occlusal surface.This material comes from the Cerro Lisandro Forma-tion at the Cerro Bayo Mesa (426,432) and the Cerros Colorados localities.†Ptychoceratodontinae (Martin, 1982) nov.comb.†Ptychoceratodus Jaeckel, 1926 Type species.†Ptychoceratodus serratus (A gassiz 1838).
Modified definition.Ceratodontiform dipnoans more closely related to †Ptychoceratodus serratus than to †Ceratodus sturii.The taxon was evaluated only for species of Ptychoceratodus but further phylogenetic analyses could show ther genera as included here.o Modified diagnosis.Calvarian bones distribution: three bones in medial and mediolateral se-ries; posterior calvarium formed by I, AB; calvarium emarginated only on its posterior edge; occlusal perforations distributed mainly among the ridge crests; four acute ridge crests in the lower tooth plates; fourth ridge crest on lower tooth plate present and well developed.†Ptychoceratodus cionei sp.nov.
(Fig. 3 A, B) Diagnosis.Mid-sized (see  in †Ptychoceratodus cionei is similar to †P. madagascariensis (=Ferganaceratodus of Mar-tin et al., 1999) in having an obtuse lingual angle and smooth ridge crests not directed anteriorly (Martin, 1982).It shares with †P.wichmanni (see description) only four ridge crests (instead of five) on upper tooth plates.Additionally, P. cionei differs from P. wichmanni in being more robust and in having the cleft between the ridge crests shallower.
Referred material.Wichmann (1924: Plate VII, fig. 6;1927:  nov.(Fig.3 C -D) Additional material.Several isolated tooth plates referred to the same species as that from the Los Alamitos Formation come from equivalent units at Arroyo Yaminué, Trapal-có and several localities where the Allen Formation is exposed (Río Negro Province; Wichmann, 1927).Additional material comes from southern Mendoza localities (e.g.Ranquil-Co; González Riga, 1999) of the Loncoche Formation (also equivant to the Los Alamitos Formation).
Diagnosis.Mid -sized (see Table I).Upper and lower tooth plates with four ridge crests.Lower tooth plates have sharp long and thin ridge crests.The first is very elongate, and the fourth is osteriorly directed.p Etymology.After Dr. Ricardo Wichmann, the early twentieth century geologist who made important contributions to the study of the referred rea.

le a
Description.Tooth plates with narrow and acute crests.Clefts between the ridges are narrow and deep.The labial profile of the crests is not steep.
The plates of †P.wichmanni were originally referred by Martin (1982) and Cione (1987) to the species « †Ceratodus» iheringi ( †Ameghino ceratodus iheringi herein).†P.wichmanni, how-ever, is larger than †A.iheringi (see Table 1) and has deep and abundant occlusal pits and broad, low and acute ridge crests absent in †Ameghi-noceratodus.Additionally †P.wichmanni shows a strongly convex lingual margin of the tooth plates.We would also like to point out that †P.wichmanni is the most common dipnoan species present in Campanian -Maastrichtian beds from Argentina.

Other ptychoceratodontids
Recorded ptychoceratodontids include the material 506 (Figs. 4d,f,h,i), considering the acute crests and well developed crunching surface.This material comes from the Cerro Lisandro Formation at the Cerros Colorados south (506) and the Portezuelo Formation t the homonimous locality ( 424). a The material on Fig. 5 share very fragile and acute crests, probably a same Ptychoceratodus species, which is very comparable to †Ptychoceratodus madagascariensis (=Ferganaceratodus of Martin et al., 1999).
Neoceratodontidae Miles, 1977 Type species.Neoceratodus forsteri (Krefft,870).1 Modified definition.Ceratodontiform dipnoans more closely related to Neoceratodus rsteri than to †Ceratodus sturii (Fig. 6).fo Modified diagnosis.Double prearticular sulcus; seven upper tooth ridge crests; more than six lower tooth ridge crests (reversed in M. wollastoni, but present in other †Metaceratodus species, such as M. bonei).(Chapman, 1914) (Fig. 3 E) Type species.†Metaceratodus wollastoni The first crest is relatively long and thin, with a marked slope.The crests are nearly straight and radiating, and the fourth crest is the shortest.Occlusal pits are well developed and are mainly disibuted over the crests.Occlusal surface is flat.
Comments.The genus †Metaceratodus is considered here to be the sister group of †Mioceratodus + Neoceratodus (Neoceratodontidae), not of †Ceratodontidae (Schultze, 1992; contra Kemp, ?Lepidosirenidae (MPCN-PV 1-6) (Fig. 3 F-H).A fragmentary dipnoan tooth plate was collected from the Anacleto Formation at Río Ne-gro Province.It preserves only the anterior two ridges.The anteroposteriorly flattened ridges end in vertical transverse crests that follow a perpendicular plane respect to the skull.This material belongs to a different kind of dipnoan, probably a lepidosirenid.1997).†Metaceratodus tooth plates differ mainly because in †Metaceratodus the first ridge crest on lower tooth plates is subequal to the lingual margin, whereas in remaining Neoceratoontidae it is much shorter.d †Metaceratodus is present from the Lower Cretaceous to the Pliocene of Australia (see Kemp, 1997).Here we refer the Argentinian material to †Metaceratodus (as previously proposed by Kemp, 1997) on the basis of the following combination of characters: robust ridge crests that originate medially, more than four ridge crests on lower tooth plates, first crest of lower tooth plates acute, occlusal pits wide and deep.
dditionaly, ridge crests are more acute in

DISCUSSION
O n the systematic value of tooth plates From 1899 to 1996, a single tooth plate represented the ceratodontiform record in Argen-tina from the Coniacian (Ameghino, 1899) and other fragments from the Campanian-Maas-trichtian (Wichmann, 1924;1927;Cione, 1987).In years to follow, our understanding of the stratigraphic record has greatly increased and today we have information on a substantial por-tion of the Late Cretaceous (Fig. 1b).The record of lungfishes is still restricted to findings from the Cenomanian of the Candeleros (Apesteguía et al. 2001) and the Cerro Lisandro Formations (Apesteguía et al., 2001;Coria et al., 1996 (Kemp, 1997).
Distinguishing supraspecific taxa of lungfishes based on isolated tooth plates is difficult (Kemp & Molnar, 1981).In fact, Kirkland (1988) states that dipnoan taxa cannot be defined by means of tooth plates and that the skull roof is essential for generic classification (Kirkland, 1988;Schultze, 1991).Intraspecific variation in tooth plate morphology (i.e.number of ridges, and the related presence or absence of a poste-rior heel) noted by Kemp and Molnar (1981) has been attributed to growth.Additionally, Churcher (1995) maintains that the formation of deep grooves with acute angles between the ridge crests and chewing movements in relation to a hard diet could induce the occlusal surface marks.However, as Campbell & Barwick (1990) pointed out, tooth plates are directly correlated to skull and mandible morphology, and they together can be useful for indicating position ithin lineages.w Much of the available fossil material for ceratodontiforms consists of isolated tooth plates.Therefore, in order to optimize the knowledge on ceratodontiform phylogeny, our work supports the inclusion of characters present in tooth plates.Tooth plates from Los Alamitos and La Colonia Formations are available in abundance, allowing several tooth plates to be analyzed from a single locality in order to recognize the most consistent features.Ideally, more characters (i.e.cranial and post-cranial) would contribute more understanding to an analysis, but we and other researchers (Martin, 1982;Martin et al. 1999) consider tooth plates to offer an abundant source of information that should not be ignored.

B iogeography
In addition to obvious differences in size, mobility and routes of dispersion, ceratodontiform dipnoans have a similar regional and stratigraphical distribution to that of †titanosauriform sauropods, which have a vast Jurassic and early Cretaceous record in North America through the Cenomanian (Bonaparte 1986).Ceratodontiforms and †titanosauriforms were considered extinct at the early late Cretaceous of North America.However, they reappeared during the Maastrichtian before their final ex-tinction within Laurasia at the end of the Mesozoic.The North American Maastrichtian dipnoans (Parris et al ., 2001) and titanosaurs (Gilmore, 1922), seem to prove a South American origin based on their continuous record from the Cenomanian through the Maastrichtian in outhern Continents.S With the exception of those found in the early Paleocene of Bolivia (Schultze, 1991), there is no record of ceratodontiforms in the South Ameri-can Tertiary.Pascual & Bondesio (1976) proposed that the †ceratodontid extinction in Patagonia likely resulted from an inability to migrate north to warmer regions when the climate changed.The authors also discuss a connection between Patagonia and Australia through Antarctica based on similarities between the Australian lungfish Neoceratodus forsteri and the Pata-gonian species †Ameghinoceratodus iheringi.Pascual & Bondesio (1976) also noted the pres-ence of †Metaceratodus wollastoni and several species of †Ptychoceratodus in both landmasses.Therefore, we do not reject the hypothesis of a connection between Patagonia and Australia even though we consider †Ameghinoceratodus and Neoceratodus to be istantly related taxa.d Members of †Ptychoceratodontinae, may have had a wide pre-Cretaceous distribution throughout greater Gondwana (Apesteguía, 2002) including India, Madagascar, Australia and possibly Antarctica, where they currently have not been recovered (Martin et al. 1999).The occurrence of ptychoceratodontines in South America begins by the Campanian-Maastrichtian transgression or perhaps earlier (Fig. 5d,f,h,I; Fig. 6).Thus, it is probable that the different spe-cies of †Ptychoceratodus from the Campanian-Maastrichtian of Patagonia represent a later invasion from India, Madagascar, or Australia hrough Antarctica).(t Most pre-Campanian Cretaceous dipnoans from Argentina represent both endemic South American lineages (e.g., †Chaoceratodus; †Ameghinoceratodus) as well as relicts of widely distributed Jurassic ceratodontiforms (e.g., †Ceratodus sp.).We also see that Cretaceous post-Campanian dipnoans are dominated by possibly immigrant forms (e.g.ptychoceratodontines, †Metaceratodus) and poorly represented endemic lineages (e.g.†Ameghinoce-ratodus).A similar faunal pattern has also been reported for other vertebrate groups (Bonaparte, 1986).

P aleobiological considerations
The rock units relevant to the «Lacustrine Senonian» are considered to be the first stages in the progressive flooding that formed the epeiric Kawas sea (Casamiquela, 1978).The ma-rine nature of these outcrops was mainly based on the presence of batoid fishes and plesiosaurs (e.g.Gasparini & De la Fuente, 2000) .Further-more, the freshwater and terrestrial taxa also recovered in the same beds were considered as allochtonous additions although they lack any ign of transport.s The batoids present in several units of the «Lacustrine Senonian» (e.g.Los Alamitos and Loncoche Formations) actually pertain to the freshwater family Rhinobatidae (A. Forasiepi, pers. comm.;Gayet, 1992).Furthermore, the plesiosaur record does not necessarily imply marine sediments, as they have occasionally been found in freshwater sediments (R. Molnar, pers.comm.).Additionally, several other faunal remains indicating a freshwater environment (e.g.Chelidae turtles, freshwater gatropods; Gasparini & De la Fuente, 2000;A. Forasiepi, pers. comm.)ave been recovered.ceratodus; Martin et al., 1999) based on the presence of only four ridge crests in the tooth plates and the ontogenetic formation of a chewing surface.Although is not possible to follow developmental patterns of these extinct dipnoans, adult morphology is in agreement with this interpretation and thus we consider P. wichmanni and P. cionei as closely related to the P. madagasariensis species group (sensu Martin, 1982). h The ceratodontiforms from the «Lacustrine Senonian» appear to be common in the sediments prior to the marine transgression and Casa-miquela (1978) proposed that they were tolerant to brackish waters, in contrast with the strict freshwater living forms.Schultze (1991) proposed that extinct ceratodontiforms could be good swimmers and that they could undertake exten-sive sea voyages, which may explain their wide distribution in the Late Cretaceous.However, dipnoans disappeared abruptly during the first stage of the marine Turonian transgression of the Western sea in North America (Eaton & Kirkland, 1999).Just as in Patagonia, dipnoans disappeared from the record when the Kawas sea flooded the continent, as evidenced by the faunal content of the clearly marine Upper section of the Los Alamitos Formation (and equivalents; Andreis, 1987).The freshwater environments inhabited by extant dipnoans, plus the fluvial pre-Campanian sediments of the Cretaceous South American ceratodontiforms, supports the conclu-sion that the «Lacustrine Senonian» forms inhabited freshwater environments.

c
In this paper two new genera endemic to South America, †Chaoceratodus and †Ameghinoceratodus, are considered basal to the «modern» clade of dipnoans, termed here as Ceratodontoidea, which includes the families †Ceratodontidae ( †Ceratodontinae + †Ptychoceratodontinae) and Neoceratodontidae.The lat-ter mily is composed by †Metaceratodus and fa †Mioceratodus + Neoceratodus, which are characterized by a double prearticular sulcus and an increasing number of ridge crests per tooth plate.†Metaceratodus was considered by other authors as belonging either to the family †Ceratodontidae (Kemp & Molnar, 1981;Kemp, 1997) or Ptychoceratodontidae (Martin, 1982) .However, these authors based their hypothesis mainly on plesiomorphic traits (e.g.medial origin of ridge crests, upper tooth plates close or contiguous, upper symphysis oblong) that are widely distributed among dipnoans (e.g.Lepidosiren, Saenodus;Fernández et al. 1973;Kemp, 1996).g Some authors (Kemp, 1998;Martin et al. 1999) proposed that both †Ceratodontidae and Ptychoceratodontidae were closely related clades.In this paper we agree with previous interpreta-tions and we include both groups as subfamilies within the single family †Cerato-dontidae.

Fig. 1 .
Fig. 1. A. Map of South America showing fossiliferous localities.Patagonian region into the box shows the localities that provided dipnoan remains, identified with the following numbers: 1, Ranquil Có; 2, Sierra del Portezuelo; 3, Paso Córdova; 4, La Buitrera; 5, Ingeniero Jacobacci; 6, Los Alamitos; 7, Paso del Sapo; 8, La Colonia; 9, Mata Amarilla.B, Stratigraphic column showing the aproximate levels of ceratodontiform findings and the bearing units in the studied region.Shaded tooth plates do not represent any special taxon.D and F include also findings outside the Neuquén Group areal distribution.The inclusion in the stratigraphic column is only for reference.C, Paleogeographic reconstruction of the southernmost tip of South America during Santonian to Early Campanian times, before the Kawas Sea ingression (modified from Apesteguía, 2002) .Lettering repre-sent the dipnoan findings related to the bearing stratigraphic level; aulacogens are corrected; valley shapes and coastal details are not rigorous.

†Chaoceratodus gen. nov.
The tooth plate is subtriangular, with four robust and short ridge crests.Clefts between the ridges are wide and shallow.The labial profile of the crests is not steep and ends in a single last crest.The first crest is long and broad, without a marked slope.The crests are relatively straight and radiating.The fourth crest is very large when compared with the second and the third.Occlusal pits are nearly absent on the occlusal surface.There are large tubercles in the labial edge of the crests except in the first where e tubercle is located toward the central region.

Table 1 .
Measurements (in mm) of fossil tooth plates.Description.Upper tooth plates with five ridge crests, whereas the lower have only four.Each crest is narrow and slender.Clefts corresponding to ridges are narrow and deep.The labial profile of the crests is steep and ends in a single vertical ridge.The first crest is relatively long and thin, with a marked angle on the labial side.All crests can be curved, though the degree of curvature may vary.
The fourth crest is usually long (when compared with other ceratodontiform genera, e.g.†Ceratodus).The lingual profile could be straight or lightly concave.Occlusal pits are nearly absent.†Ceratodontidae Gill, 1872 Type species.†Ceratodus latissimus Agassiz, 838. 1 Modified definition .Ceratodontiform dipnoans ore closely related to †Ceratodus sturii and m †Ptychoceratodus serratus than to Neoceratodus rsterii.fo Diagnosis.JLM descendant process absent; posterior calvarium formed by YZ, JLM, I, ABC; short ridge crests on tooth plates; upper symphysis oblong, lower symphysis linear; Four to five dge crests on lower tooth plates.s

nov. comb.
Revista del Museo Argentino de CienciasNaturales, n. s. 9 (1), 2007 †Ceratodus argentinus sp.nov.(Fig. 2 F) Diagnosis.Mid-sized (see Table I).Upper tooth plates with five ridge crests.The third crest is larger than the fourth.The plate becomes thin-The tooth plate is low, subtriangular, with four robust, short crests.A fifth crest is present though reduced in size.Clefts between the ridges are wide and shallow.The labial profile of the crests is not steep and ends in a heel.The crests are subequal in size and morphology, nearly straight and radiating.Occlusal pits are sparse and are istributed mainly between the crests.d †Ceratodus argentinus is similar to † C. concinnus (sensu

Table I
The tooth plate is subtriangular, with four robust and acute crests.Clefts between the ridges are wide and deep.The labial profile of the crests is steep and ends in a single last crest.