Paleocharacodon guzmanae gen., 2023

Caballero-Viñas, Carmen, Alvarado-Ortega, Jesús & Severiano, Kleyton Magno Cantalice, 2023, A Pliocene goodeid fish of the Paleolake Amajac, Sanctórum, Hidalgo, Mexico, Palaeontologia Electronica (a 30) 26 (2), pp. 1-39 : 27-32

Paleocharacodon guzmanae , a New Goodeinae

Paleocharacodon guzmanae gen. and sp. nov. is also an undeniable member of Goodeinae because it was a viviparous species and shows both the homoplasy and synapomorphy that support this subfamily (8 and 9 in Figure 15 , Table 4). Following the numbering of the anterior paragraph, these features include: 8) The anterior anal fin ray is rudimentary

(Parenti, 1981, figure 83, node B) ( Figure 13 ). 9) The andropodium or pseudophallus is present and formed by the unbranched anterior anal-

fin rays that crowd together ( Figure 13 ), separated by a notch from the rest of the fin, and reduced between 50-80% concerning the subsequent posterior rays; Webb (1998, p. 75,

ch. 684 in part) discovered this remarkable osteological synapomorphy. Additionally,

Webb (1998, p. 61 and 92, ch. 637) suggested that the appearance of a shallow neurocranium (in which the height is equal to or less than half of its width) also supports the

Goodeinae monophyly; however, this condition may represent a plesiomorphy because it is present in Empetrichthyinae and other

Cyprinodontiformes , too.

Eight osteological features support the naturalness of Empetrichthyinae . These include four synapomorphies (11-18 in Figure 15 , Table 4), previously noticed by Parenti (1981) and Webb (1998). Paleocharacodon guzmanae gen. and sp. nov. differ from Empetrichthyinae because it does not have any of its diagnostic features. Following the numbering of the anterior paragraphs, these features include: 10) The lack of the pelvic fin and girdle

(Parenti,1981, node C in figure 83; Webb,

1998, ch. 673). On the contrary, the pelvic fin and girdle are well-developed in P. guzmanae

( Figure 12 ). 11) The epibranchial 1 is nearly Y-shaped,

notched at its base, and has a lateral process

(Parenti, 1981, node C in figure 83 and figure

47B; Webb, 1998, ch. 668). Unfortunately, the epibranchials are unknown in P. guzmanae ,

but among goodeines this bone is rod-

shaped.

12) The surface of neurocranial, suspensorium, and hypural bones are rugose and irregular due to pits and ridges (Webb, 1998, ch. 643). On the contrary, these bones are superficially smooth in P. guzmanae ( Figures 3-7 , 8D , 14 ).

13) The anterior margin of the vomer is abruptly concave medially (Uyeno and Miller, 1962; Webb, 1998, figure III.9C, ch. 629). Sadly, the vomer is unknown in P. guzmanae .

14 and 15). The frontal has a supraorbital canal partially ossified and does not show the break 4a-4b (Gosline, 1949; Fitzsimons, 1981; Webb, 1998, chs. 632 and 634) ( Figure 15 ). On the contrary, as in other goodeines, in P. guzmanae , the frontal bone entirely encloses the supraorbital canal that shows the break 4a-4b ( Figure 7 ).

16) The dorsal and ventral pharyngobranchials are relatively robust; their bases are deep, ossified, and higher than their teeth (Webb, 1998, ch. 667). Although in P. guzmanae , the toothed pharyngobranchial plates are not well-exposed, in this species, such plates are rather gracile and bear large teeth of varying size, usually rest unattached and scattered; here, the most prominent pharyngobranchial teeth are higher than the pharyngobranchial plates.

17) Third postcleithrum with a posteriorly directed laminar plate at its mid-length (Webb, 1998, ch. 672). P. guzmanae has only two postcleithra.

Palaocharacodon guzmanae and Other Goodeines

Paleocharacodon guzmanae gen. and sp. nov., Goodiini , Characodon , Xenotaenia , and some species of Allotoca share a primitive feature; the dorsal fin is far in the back of the body (the predorsal length is equal or greater than 67% of SL). Hence, P. guzmanae differs from Ilyodontini, Girardichthyini (less some species of Allotoca ), Chapalichthyini (including Zoogoneticus and less Xenotaenia ), and Skiffia that have the dorsal fin located not so far back (the predorsal length is equal or less than 67% of SL)

18) (in Figure 15 , Table 4) (Miller, 1948; Webb,

1998, p. 77, ch. 689).

According to Webb (1998, p. 61, ch. 637), all goodeines except Goodiini, Ilyodontini , and Alloophorus show a neurocranium primitively low; in the posterior view, its height/width ratio is 0.45 to 0.52. On the contrary, in other goodeines, the neurocranium shows a higher derived condition, and the range of such proportion is 0.58 to 0.66 (19 in Figure 15 , Table 4). This character had a regressive change to the shallow state in Ilyodontini and Alloophorus 19*) (in Figure 15 ). Unfortunately, the neurocranial proportions of Paleocharacodon guzmanae gen. and sp. nov. and Tapatia occidentalis are unknown.

Into Goodeidae , only Goodiini and Empetrichthyinae possess rostral cartilages (Webb, 1998, p. 63, ch. 644). Other goodeids have no rostral cartilage 20) (in Figure 15 , Table 4). The presence or absence of this cartilage is unknown in Paleocharacodon guzmanae gen. and sp. nov. and

Tapatia occidentalis .

According to Webb (1998), Goodea and Ataenobius form the tribe Goodiini . In one of his hypotheses, this tribe is the sister group of other goodeines, while in the other, this constitutes a natural group with Skiffia . Two unambiguous characters, a synapomorphy, and a homoplasy, support this tribe in Webb's hypotheses. The first is the presence of lateral wings in the anterior end of the parasphenoid

21) (in Figure 15 and Table 4; Webb, 1998, p. 61, ch. 638). The homoplasy is the presence of a pelvic fin relatively short because its posterior edge does not reach the dorsal fin origin

22) (in Figure 15 and Table 4; Webb, 1998, p. 72, ch. 675). A short pelvic fin is also present in Characodon and Allotoca (see Domínguez-Domínguez et al., 2005, p. 545, 547). In other goodeids, the parasphenoid has no wings because its anterior lateral edges are parallel,

and the pelvic fin is long and goes beyond the dorsal fin origin. Although the pelvic fin of

Paleocharacodon guzmanae gen. and sp.

nov. is short, it is recognized as non-Goodiini fish because its parasphenoid is not winged.

In Webb’s (1998) hypotheses, the long and well-developed posterior process in the epioccipital bone represents a derived condition of Goodiini and Skiffia 23) (in Figure 15 and Table 4; Webb, 1998, p. 62,

ch. 640). These taxa, Ilyodontiini (except

Allodontichthys polylepis , A. tamazulae , and

A, zonistius ), Ameca , and Xenoophorus have

20 to 54 gill rackers on the first branchial arch 24) (in Figure 15 and Table 4); Webb, 1998, p. 70,

ch. 665). In other goodeids, the epioccipital process is tiny, and the first branchial arch has only 9 to 19 gill rackers. Unfortunately, Paleocharacodon guzmanae gen. and sp. nov. and

Tapatia occidentalis do not expose either of these features.

25 and 26) (in Figure 15 and Table 4; Webb, 1998,

chs. 645-647, respectively). The crowns of primary jaw teeth are distally flattened, bicuspid,

and straight or broadly blunted, and its bases are loosely attached to the jaws by cartilage in

Goodiini , Skiffia , Ilyodon , and Xenoophorus also shows (e.g. Hubbs and Turner, 1939). On the contrary, other goodeids and Paleocharacodon guzmanae gen. and sp. nov. (Figures 8, 10, 11) have primary jaw teeth bicuspid, acute, which bases are co-ossified with the bone of jaws. According to Webb

(1998), Allodontichthys shows tricuspid or shouldered teeth and large specimens of Skiffia multipunctata also have strong tooth attachments.

27) (in Figure 15 ; Smith, 1980, figure 17B; Guzmán, 2010, figure 9; Webb, 1998, p. 66, ch. 654). On the contrary, Paleocharacodon guzmanae gen. and sp. nov. and other goodeids show the alternative primitive condition of this bone; its dorsal process is projected dorsally and forms an angle of about 90° with its anterior process ( Figure 6 , 8B , 10 ).

Among goodeids the ventroposterior coracoid region is variable (Webb, 1998, p. 71-72, ch. 671). This region shows a straight angle in Empetrichthyinae , most Goodeiinae, and probably in Tapatia occidentalis ; on the contrary, in Skiffia , this is broadly convex

28) (in Figure 15 and Table 4), and in Ilyodon varies between straight and convex. Only in Ameca , Xenotoca variata , and now Paleocharacodon guzmanae gen. and sp. nov, this region is convex, has a posterior margin vertically tilted, and is anteriorly limited by a narrow and deep notch ( Figure 6 ; Webb, 1998, figure III.27). In this case, the condition shared by Ameca , X. variata , and P. guzmanae seem an evolutive convergence.

Furthermore, Webb (1998, p. 67-68, ch. 657) noted that in Goodiini and Skiffia , the palatoquadrate arch (between the articular heads of the palatine and quadrate bones is about vertically inclined 29) (in Figure 15 and Table 4). On the contrary,

this arch is bent forward in other goodeids,

including Paleocharacodon guzmanae gen.

and sp. nov. ( Figure 8D ).

Likewise, Goodiini , Skiffia , Ilyodon , and Ameca share a homoplasic and derived feature, the retroarticular bone forms the lingual part of the articular facet for the quadrate 30) (in Figure 15 and Table 4; Webb, 1998, p. 67,

ch. 655). On the contrary, this bone does not form that facet in other goodeids. In Paleocharacodon guzmanae gen. and sp. nov., that facet has a donut-like configuration in which the retroarticular forms its central region and the anguloarticular has two curved processes forming its surrounding part ( Figures 6 , 8B ).

Although this donut-like configuration of the articular facet for the quadrate (added in this work as: character 31 in Figure 15 and Table 4) was observed only in specimens of Characodon ,

additional observations are required to clarify its possible occurrence in other goodeids.

Based on Webb’s hypotheses, among goodeids, there is a primitive anterolateral projection in the palatine head of Empetrichthyinae , Goodiini , Ilyiodontini, and most Chapalichthyini (except for Alloophorus , Zoogoneticus , and Skiffia francesae ). A convergent derived state of these characters, the lack of such projection in the palatine occurs in Characodontini , Girardinichthyini, Alloophorus , Zoogoneticus , and S. francesae 32) (in Figure 15 and Table 4, Webb, 1998, p. 67,

ch. 656). Herein, Paleocharacodon guzmanae gen. and sp. nov. and is excluded from Chac-

arondontini and Girardinichthyini because it shows the primitive anterolateral projection of the palatine.

Herein, we identify that Paleocharacodon guzmanae gen. sp. nov. and Characodon spp. Differ from each other in at least three different features. In the last, the openings of the supraorbital canal show a formula —1-2a, 2b-7— as in some Allodontichthys species (Fitzsimons, 1981, table 1); its posttemporal is unforked because the anteroventral process is absent as in Empetrichthyinae , Girardichthyini, and Zoogoneticus (33 in Figure 15 and Table 4; Webb, 1998, p. 71, ch. 669); and the parasphenoid bone shows outstanding dorsal wings extended in its orbital part. On the contrary, in the fossil species, the openings of the supraorbital canal show a formula never recorded before among goodeids —1-2a, 2b-3a, 3b-4a, 4b-5a, 5b- 7—( Figure 7 ); its parasphenoid bone shows tiny ventral and lateral wings in its orbital part, ( Figure 6 ); and its posttemporal bone shows a small anteroventral process that may be an intermediate condition observed in other goodeids ( Figure 6 ).

Unfortunately, in his hypotheses, Webb (1998), most no-Goodiini, and no-Characodontini groups do not have osteological supporting features. Therefore, it is not easy to compare the anatomy of such groups with those features observed here in Paleocharacodon guzmanae gen. sp. nov. In the present context, after mapping the osteological features of P. guzmanae into Webb’s hypotheses, it is possible to point out that this fossil is part of the family Goodeidae and the subfamily Goodeinae (it shows the characters 1-6, 8-9 in Figure 15 ). In addition, the mixture of characters of this fossil goodeid does not allow us to recognize it as part of any of the tribes of Goodeinae . Besides, this fossil goodeid does not share features with the tribes and shows different characters to those that support such tribes or groups of tribes (numbers in italics in Figure 15 ). On the other hand, this fossil and the tribe Characodontini shared more features (numbers in bold in Figure 15 ), but it shows significative differences with its single member, Characodon . Therefore, the species described here was included in its genus, Paleocharacodon , to highlight its similarity with Characodon , including a feature observed for the first time, the donut-like articular facet for the quadrate.

Phylogenetic and Biogeographic Implications

Despite numerous recently published hypotheses (Doadrio and Domínguez, 2004; Webb et al., 2004; Domínguez-Domínguez et al., 2010; Foster and Piller, 2018), the phylogenetic and biogeographic relationships of Goodeidae are still unclear ( Figure 15 ). This situation probably results from the lack of suitable fossil evidence that allows us to recognize the history of the morphological changes of Goodeidae , as well as the geological-environmental conditions in which they occurred. The discovery of Paleocharacodon guzmanae gen. and sp. nov. not only complements our knowledge about the diversity of the family, but it also reveals itself as an element to consider in future biogeography studies.

The accurate osteological description of living goodeids is a pending task that avoids the comparison of its extinct and recent species. Despite this, the analysis of Paleocharacodon guzmanae gen. and sp. nov. and some data published of other goodeids reveals that this new fish does not belong to any goodeine tribes. The putative primitive features of P. guzmanae suggest that it may represent a primitive goodeinae . Such observation is congruent since P. guzmanae is a Pliocene species of at least 4 Mya. In any case, assessing the relationships of fossil goodeids, such as P. guzmanae , Goodea -like from Sanctórum, and Tapatia occidentalis requires a comprehensive phylogenetic study involving osteological data of recent and fossil goodeids.

In the biogeographic hypotheses of Goodeidae so far proposed, Goodeinae arose in the northwestern region of Mexico and had different episodes of diversification in the central part of this country. Such diversification seems more successful in rivers and lakes of the western and southern of the country, which today concentrate most of the known species. Later, some of its genera experienced exchanges between these regions (Gesundheit and Macías, 2005; Domínguez-Domínguez et al., 2006, 2010; Pérez-Rodríguez et al., 2015, Foster and Piller, 2018; among others). The finding of Paleocharacodon guzmanae gen. and sp. nov. and his contemporary Goodea -like in Sanctórum is significant. The Pliocene strata of the extinct Paleolake Amajac are within the domains of the Pánuco-Salado Basin on the eastern side of Mexico, where there are only six recent species ( Table 3, Figure 16 ). The contrasting diversity of goodeids between the western-southern and eastern regions of Mexico seems linked to the geological-environmental history of the country. On the one hand, during the Neogene, the development of the TMVB strongly and continuously affected its western and southern regions, while the eastern area occupied by the Pánuco-Salado basin was relatively more stable. For now, the uncertain relationships of P. guzmanae within the goodeids hinder the recognition of whether this supports or rejects the biogeographic hypotheses already proposed; however, our study suggests that this extinct species of the eastern slope of Mexico is not directly related to any species from the Pánuco-Salado Basin.

Additionally, divergence dates in the Goodeidae evolution are available in the most recent phylogenetic studies ( Figure 15 ); Foster and Piller, 2018; however, the discovery of Paleocharacodon guzmanae gen and sp. nov. suggests that a different goodeinae lineage without living representatives must have existed. According to these data, the family Goodeidae and the subfamilies Goodeinae and Empetrichthyinae rose during the early Miocene, before 15 Mya; in the later 5 My and during the middle Miocene, between 15 and 10 Mya, the goodeines tribes separated; and finally, since then the diversification of these fishes led to the establishment of all genera and species hitherto known. As demonstrated in the previous section, the available evidence from Tapatia occidentalis and P. guzmanae indicates that these Miocene and Pliocene fossil species are part of

CABALLERO-VIÑAS ET AL.: PLIOCENE GOODEID FROM MEXICO

Goodeinae . However, their inclusion at the tribe level is impossible and may represent unknown members of other lineages.

The situations described in the two previous paragraphs suggest that the biogeographic history of goodeids is more complex than those described so far. Such a process may include at least two alternative early scenarios: A) Early goodeids were widely distributed in Mexico and B) The eastern slope of Mexico received an ancient group of goodeids from the northwest region, subsequently displaced by more recent species.

The geographic distributions of Goodeidae and Profundulidae are disjoint, adjacent, and separated by the Sierra Madre del Sur. The first family inhabits the north, between the southwestern USA and the Mesa Central of Mexico, plus its neighboring regions. At the same time, Profundulidae is found further south, from the Pacific slope of the Sierra Madre del Sur and the Mixtec Basin to Guatemala, El Salvador, and Honduras (Morcillo Alonso, 2004, figure 1). Such distributional patterns respond to the development of TMVB, which began 10-20 million years ago. In this scenario, fossils of Paleocharacodon guzmanae gen. and sp. nov. are geographically nearer to the current distribution of Profundulidae and temporally closer to the origin of TMVB; however, its importance in the effort to understand the separation of these two families is minimal because Profundulidae has no fossil record.

Figures

FIGURE 3. IGM 13117, holotype of Paleocharacodon guzmanae gen. and sp. nov., a pregnant female specimen from the Pliocene lacustrine sediments of the Paleolake Amajac, Sanctórum, Atotonilco El Grande Municipality, Hidalgo, central Mexico. A) Part of the specimen observed in white light. B) Part of the specimen observed under UV light. C) Counterpart of the specimen observed under UV light.

FIGURE 4. Paratypes of Paleocharacodon guzmanae gen. and sp. nov., from the lacustrine sediments of the Paleolake Amajac, in Sanctórum, Atotonilco El Grande Municipality, Hidalgo, central Mexico, observed under UV light. A) Part of IGM 13120, a male specimen. B) Part of IGM 13121, a male specimen. C) Part of IGM 13125, a female specimen.

FIGURE 5. Details of IGM 13125 (part), paratype of Paleocharacodon guzmanae gen. and sp. nov., from the lacustrine deposits of the Paleolake Amajac, in Sanctórum, Hidalgo, central Mexico. A) Head observed under white light. B) Unborn fishes preserved in the abdominal cavity, observed under UV light. Abbreviatures: fr, frontal; la, lacrimal; let, lateral ethmoid; psp, parasphenoid (note its anterior end, bifid and with no lateral expansion); black arrows show articulated vertebrae of unborn fishes; red arrows show the pectoral fin of an unborn fish.

FIGURE 6. μCT imagens of IGM 13127, paratype of Paleocharacodon guzmanae gen. and sp. nov., from the lacustrine sediments of the Paleolake Amajac, in Sanctórum, Atotonilco El Grande Municipality, Hidalgo, central Mexico. A) Left side of the head and anterior part of the trunk. B) Quadrate and bones of both jaws exposed on the right side. C) Close-up of bones involved in the articulation quadrate-lower jaw showing the bilobed head of the quadrate and the articular facet of the anguloarticular in which there is a central participation of the retroarticular (here disarticulate and displaced from its normal position) and two enveloping projections of the anguloarticular. D) Right view of the hyoid arch. The scale only applies to A, B and D. Abbreviations: 1, 2a, 2b, 3, pores of the supraorbital sensory canal; aa, anguloarticular; bh, basihyal; br, brachiostegal ray; bst, bicuspid sharp tooth; cha, ceratohyal anterior; chp, ceratohyal posterior; cl, cleitrum; co, coronomeckelian; id; cor, coracoid; d, dentary; dsp, dermosphenotic; entp, entopterygoid; epi, epioccipital; fr, frontal; hy, hyomandibula; ih, interhyal; iop, infraopercle; let, lateral ethmoid; mx, maxilla; na, nasal; op, opercle; pa, parietal; pcli, postcleitrum inferior; pmx, premaxilla; pop, preopercle; psp, parasphenoid; ptt, posttemporal; q, quadrate; r, rib; rar, retroarticular; scl, supracleitrum; soc, supraoccipital; sp, sphenotic; sop, subopercle; sy, symplectic; uh, urohyal; ust, unicuspid sharp tooth; utt, unicuspid truncated tooth; vhh, ventral hypohyal; dubious elements; within parenthesis: i, internal view (if it is not indicated, the structures show the right view); l, left; r, right; va, ventroanterior view; vp, ventroposterior view.

FIGURE 7. Close-up of IGM 13130, a specimen of Paleocharacodon guzmanae gen. and sp. nov. of unknown sex. A) Disarticulated bones of the head under white light. B) Line drawing based on A. Abbreviations: fr, frontal (dorsal surface); let, lateral ethmoid (lateral surface); mx, maxilla (dorsal surface of the proximal end); psp, parasphenoid (dorsal surface of the ocular part); 2b, 3a, 3b, 4a,4b, 5a, 5b, 6, and 7 are the openings of the supraorbital canal preserved in the frontal.

FIGURE 8. Osteological details of Paleocharacodon guzmanae gen. and sp. nov., from the Paleolake Amajac deposits, Sanctórum, Mexico. A) Close-up of the right side of the head of IGM 13118 showing the medial surface of the left otoliths. B) Left anguloarticular bone of IGM 13121 showing the articular facet for the quadrate formed by a surrounding C-shaped process (note this in the shadow below), as well as the central participation of the retroarticular bone that here is empty (see the red line) because this bone is not preserved. C) Right dentary bone and associated teeth of the part of IGM 13121. D) Suspensorium of IGM 13123. E) Dorsal surface of the lateral process of right sphenotic, preserved in IGM 13130. F) Abdominal region of IGM 13130. G) Close-up of pharyngeal teeth preserved in the counterpart of IGM 13121. Abbreviations: aa, anguloarticular; aadp, anguloarticular dorsal process; aapp, anguloarticular anterior process;ast, asteriscus otolith; bst, bicuspid sharp tooth; cor, coracoid; d, dentary; d, dentary; entp, entopterygoid; epn, epineural; faq, articular facet for the quadrate; hy, hyomandibula; lap, lapillus otolith; mx, maxilla; pal, palatine (note the anterolateral projection in the head); pmx, premaxilla; pmx, premaxilla; pop, preopercle; q, quadrate; r, rib; sag, sagittal otolith; sc, scale; sop, subopercle; sp, sphenotic; sy, symplectic; ust, unicuspid sharp tooth. The red arrow in B shows the space in the articular facet for the square (which should be occupied by the retroarticular bone) surrounded by the pair of curved processes of the anguloarticular that also forms part of such facet (see also the shadow of the process)

FIGURE 10. Bones of the jaws preserved in IGM 13121, a female specimen of Paleocharacodon guzmanae gen. and sp. nov., from the Paleolake Amajac deposits, Sanctórum, Mexico. A) closeup of the anterior part of the head under white light. B) Line drawing based on A. Abbreviations: aa, anguloarticular; bst, sharp bicuspid tooth; co, coronomeckelian; d, dentary; mx, maxilla; pl, palatine; pmx, premaxilla; sop, subopercle; ust, unicuspid sharp tooth. In parenthesis i, internal view; l, left; r, right.

FIGURE 12. Pelvic fin of Paleocharacodon guzmanae gen. and sp. nov., from the Pliocene Paleolake Amajac deposits in Sanctórum, Hidalgo, Mexico. A) Preserved in IGM 13129, observed under UV light. B) Preserved in part of IGM 13121, observed under white light. Abbreviations: afpvr, articular facet for pelvic fin rays; isp, ischial process; lp, lateral process of pelvic fin bone; mp, medial pelvic; pvb, pelvic bone; pvfr, right pelvic fn ray; r, rib; (l), left; (r), right.

FIGURE 13. Impaired fins of Paleocharacodon guzmanae gen. and sp. nov., from the Pliocene Amajac Paleolake deposits in Sanctórum, Hidalgo, Mexico, observed under UV light. A) Dorsal fin of IGM 13129 (sex undefined; the distal ends branched and segmented of the dorsal rays are covered). B) Anal fin of IGM 13121 (male with anal rays 2 and 13 only preserved as impressions; since the bone of tips of these rays is not-preserved, the arrows show the anterior short rays forming the andropodium and the posterior rays forming a rounded fin). Abbreviations: afr, anal fin ray; amp, anal medial pterygiophore; app, anal pterygiophore; dfr, dorsal fin ray; dmp, dorsal medial pterygiophore; dpp, dorsal proximal pterygiophore.

FIGURE 14. Caudal skeleton of Paleocharacodon guzmanae gen. and sp. nov., IGM 13119, from the Pliocene Paleolake Amajac deposits in Sanctórum, Hidalgo, Mexico. A) Specimen observed under UV light. B) Idealized line drawing of A. Abbreviations: cc, caudal complex (= preural centrum 1+ ural 1 and 2); ep, epural; hspu, hemal spine of preural centrum; ihf, interhypural foramen; ksp, keel-shaped process; nspu, neural spine of preural centrum; ph, parhypural; pu, preural centrum; sc, scale; ssp, spine-shaped process; ur, urostyle.

FIGURE 15. Phylogenetic hypotheses of the family Goodeidae. The numbers indicate the distribution of osteological features. Underlined numbers are synapomorphies; not underlined numbers are homoplasies; bold characters are those shared by Paleocharacodon guzmanae gen. and sp. nov.; italic characters are those which P. guzmanae shows an alternative condition or state; characters in normal font are those unknown in this new species. (Continued next page.)

FIGURE 16. General distribution of recent and fossil Goodeinae species in the hydrological basins of Mexico (based on Domínguez-Domínguez et al., 2006, 2010)