Scutatuspinosus itapagipensis Santos and Corrêa, 1985

Alvarado-Ortega, Jesús, Than-Marchese, Bruno Andrés & Melgarejo-Damián, Pilar, 2020, On the Albian occurrence of Armigatus (Teleostei, Clupeomorpha) in America, a new species from the Tlayúa Lagerstätte, Mexico, Palaeontologia Electronica (a 52) 23 (3), pp. 1-30 : 20-24

Scutatuspinosus itapagipensis Santos and Corrêa, 1985 .

Sorbinichthys elusive Bannikov and Bacchia, 2000 .

Sorbinichthys africanus Murray and Wilson, 2011 .

Thorectichthys rhadinus Murray and Wilson, 2013.

Thorectichthys marocensis Murray and Wilson, 2013. Cenomanian. Namoura, Lebanon.

Hauterivian?. Marfim Fm., Brazil.

Cenomanian. Namoura, Lebanon.

Cenomanian/Turonian. Agoult, Morocco.

Cenomanian/Turonian. Agoult, Morocco.

Cenomanian/Turonian. Agoult, Morocco.

Triplomystus applegatei Alvarado-Ortega and Ovalles-Damián, 2008 . Cenomanian. El Espinal, Mexico.

Triplomystus noorae Forey, Yi, Patterson, and Davies, 2003 . Cenomanian. Namoura, Lebanon.

Triplomystus oligocostatus Forey, Yi, Patterson, and Davies, 2003 . Cenomanian. Namoura, Lebanon.

Tycheroichthys dunveganensis Hay, Cumbaa, Murray, and Plint, 2007 . Cenomanian. Dunvegan Fm., Canada. Tunisiaclupea speratus Boukhalfa, Wu, Ben Ali, and Fang, 2019 . Late Barremian. Chotts Basin, Tunisia.

contact with each other, between the supraoccipital and frontals; 3) a large beryciform foramen in the anterior ceratohyal; 4) subtriangular predorsal scutes; 5) the predorsal scutes form a series that extends only over two-thirds of the distance between the occiput and dorsal fin base (this condition is hereby referred to “the incomplete predorsal scute series”). After the inclusion of A. naumourensis and A. alticorpus in this genus, Forey et al. (2003, p. 275) emended this diagnosis to include the presence of the following additional features: 6) medial surface of entopterygoid with enlarged teeth; 7) dorsal and ventral hypohyals much deeper than long; 8) parietals carrying the supratemporal commissure within a bone-enclosed tube; 9) the base of the posterior border of the posttemporal bone is crenulated; 10) proximal radials of posterior eight or so pterygiophores in dorsal fin with expanded heads. Unfortunately, characters 1-3 and 6-8 are not exclusive to Armigatus and have been documented in other ellimmichthyiform taxa; hence, individually these have poor diagnostic value. The crenulated posterior edge of the posttemporal bone described by Forey et al. (2003) (feature 9) is not exclusive of Armigatus because it is also present in Paraclupea seilacheri (Alvarado-Ortega and Melgarejo-Damián, 2017, figure 6); in any case, A. carrenoae also has a posttemporal bone with a crenulated posterior edge ( Figure 5 ). The diagnostic usefulness of features 7 and 10 is at least questionable because Forey et al. (2003) did not provide a broader and accurate discussion; however, A. carrenoae can be definitively said to possess these ( Figures 5 , 8 ). In the present context, the most compelling diagnostic feature of Armigatus is the presence of subtriangular predorsal scutes forming an incomplete series (features 4 and 5). A.carrenoae sp. nov. is a member of Armigatus because it possesses the features 4 and 5, as well as 1-6 and 8-9 ( Figures 3-10 ).

Table 3 summarizes a comparison of the morphological features present in the nominal species already included within Armigatus . The body proportions of these species are similar except for the body height; A. oligodentatus is a comparatively gracile and elongated fish, in which the maximum body height is close to 32.1 % of SL, whereas Armigatus carrenoae sp. nov. and other species have higher bodies (the maximum body heights range between 37.2 and 51.2 % of SL). In addition, A. carrenoae shares a relatively low number of anal and dorsal fin rays (15-17 and 11-13, respectively) with A. dalmaticus (16 and 13-14) and probably with A. oligodentatus (12?-14? and 10?-13?). In contrast, these fins have more rays in A. brevissimus (28 and 19), A. namourensis (24-27 and 18- 19), and A. alticorpus (at least 25? and 15-17). In A. namourensis and A. alticorpus , there are five to six predorsals while in A. carrenoae and A. brevissimus there are always 6 of these bones. Contrastingly, A. oligodentatus and A. dalmaticus have seven to eight predorsal bones. Moreover, the number of total vertebrae is variable among Armigatus species: A. brevissimus only has 31; A. dalmaticus and A. carrenoae share an intermediate condition in which this number ranges between 33- 35 and 32-37, respectively, and A. namourensis , A. alticorpus , and A. oligodentatus have more vertebrae, between 37 and 38. Finally, A. carrenoae has only six postpelvic scutes while A. brevissimus has seven and other species have eight to 11.

Other osteological features that highlight the uniqueness of A. carrenoae sp. nov. seem to be somewhat problematic ( Table 3). On the one hand, this Mexican species, A. brevissimus , and A. namourensis show the osteoglossid-like tooth patch in the parasphenoid bone. Remarkably, this structure has not been observed in A. oligodentatus , A. dalmaticus , and A. alticorpus ( Forey et al., 2003; Murray et al., 2016, Vernygora and Murray, 2016; Vernygora and Murray, 2021). On the other hand, in A. brevissimus , A. namourensis , and A. carrenoae sp. nov. the frontal, parietal, and pterotic bones are strongly ornamented with conspicuous grooves and sinuous ridges that enclose the paths of the preorbital, temporal, and supratemporal canals, which open through some pores scattered on the surface of these bones ( Figure 5 ). Similar ornamentation of such bones is present in other ellimmichthyiforms, as Ellimmichthys , Ellimma , and Paraclupea ( Chang and Grande, 1997, figure 4). In contrast, bones of the skull roof are smooth in A. alticorpus , A. oligodentatus , and A. dalmaticus (Vernygora and Murray, 2016, 2021; Murray et al., 2016, figure 2). Additionally, at least A. carrenoae sp. nov. and A. brevissimus share the presence of short apicobasal grooves on the basal quarter of the opercular surface ( Figures 1 , 4 , 6 ). A similar opercular ornamentation is also present other deep-bodied ellimmichthyiformes, such as Ellimmichthys branneri and Paraclupea seilacheri ( Chang and Maisey, 2003, figure 4; Alvarado-Ortega and Melgarejo-Damián, 2017, figure 5). Otherwise, the opercle seems to be superficially smooth in A. oligodentatus , A. dalmaticus , and A. alticorpus (Murray et al., 2016; Vernygora and Murray, 2016, 2021). These opercular grooves are unclear in A. namourensis ( Forey et al., 2003) .

Besides Armigatus carrenoae sp. nov., both A. brevissimus and A. alticorpus also have epineurals and epipleurals associated with all centra except for the posteriormost four preurals. Hence, the most posteriors of these elongated bones almost reach the caudal peduncle ( Figures 3 , 4 , 9 , Table 3). A similar distribution of these bones seems to be present in all the species of Diplomystus and Gasteroclupea branisai ( Grande, 1982; Chang and Maisey, 1997, figure 12.A; Marramà and Carnevale, 2017, figure 5.D). In A. naumorensis , A. oligodentatus , and A. dalmaticus the epineurals and epipleurals are present only in the most anterior caudal centra, far from the caudal peduncle, and in extreme cases only are extended as far as the anal fin ( Forey et al., 2003, figure 54; Vernygora and Murray, 2016, figure 1; Murray et al., 2016, figure 1).

Finally, Armigatus carrenoae sp. nov. differs from other species of Armigatus because its predorsal scute series has anterior oval scutes, which progressively are more expanded and change to a subtriangular-shape; here, the posterior predrosal scute is the biggest and has a conspicuous posterior spine ( Figure 10 , 13 , Table 3). In Armigatus brevissimus , the anterior predorsal scutes are subtriangular while the posteriormost predorsal scutes are heart-shaped and have no posterior spine ( Figure 12 ; Grande, 1982, 1985). In A. namourensis and A. oligodentatus , the predorsal scutes seem to be uniformly heart-shaped ( Forey et al., 2003; Murray et al., 2016). Armigatus alticorpus and A. dalmaticus own the most distinctive and intriguing predorsal scutes; in the former species, these scutes are evenly subrectangular, antero-posteriorly short, extremely laterally expanded, and have no posterior spine (Vernygora and Murray, 2021, figures 7.A and 7.B) while in the latter species, such scutes are rather subrectangular, a little laterally expanded, and most of them have a posterior spine (Murray et al., 2016, figure 2).

Furthermore, in Armigatus carrenoae sp. nov., A. brevissimus , and A. alticorpus the space occupied by the predorsal scute series shows and additional distinctive condition ( Table 3); the comparatively low number of predorsal cutes (8 to 9) forms a true incomplete predorsal series, which is preceded by unmodified scales and lies close to the dorsal tips of the posterior three or four predorsal bones (Figures, 10, 12, 13; Vernygora and Murray, 2021, figure 7). In other species of this genus, the number and distribution of predorsal scutes resemble those of the complete predorsal scute series observed in other ellimmichthyiforms, such as Ellimma , Ellimmichthys , and Paraclupea ( Chang and Grande, 1997; Chang and Maisey, 2003; Alvarado-Ortega and Melgarejo-Damián, 2017; among others). Armigatus namouraensis , A. dalmaticus , and probably A. oligodentatus have more predorsal scutes (10 to 19) that cover a larger portion of the predorsal edge of the trunk, lie over all the predorsal bones, and reach a position closer to the occiput (see Forey et al., 2003, figures 51.A, 54; Murray et al., 2016, figure 2; Vernygora and Murray, 2016, figure 1).

Biogeographical Remarks

Paleontological researches in Mexico of the last 20 years have allowed the recovery of numerous fossils of clupeomorph fishes, mainly representatives of the order Ellimmichthyiformes (Than-Marchese et al., 2017) . Recently, we launched a project to know the taxonomic identity of these Mexican fossils and explore their phylogenetic and biogeographical implications. We have identified the presence of three possible new species belonging to or related to the genus Armigatus ; two of these are from the Albian deposits of Tlayúa quarry, Puebla, central Mexico, while the another one is from the Early Cenomanian strata exploited in the El Chango quarry, Chiapas, southeastern Mexico. The first of these species is described here, as A. carrenoae sp. nov., while the descriptive studies of the other two are in progress.

The discovery of A. carrenoae sp. nov. in the Albian deposits of the Tlayúa quarry represents the first record of Armigatus beyond the western realm of the Tethys Sea, in Europe, North Africa, and the Middle East, and the first record of this genus on the American continent. Moreover, A. carrenoae increases the temporal range of this genus up to the middle-late Albian ( Figure 13 ). Although the interrelationships of the species of Armigatus are under discussion by different authors, the presence of Armigatus in the eastern and western extremes of the Tethys opens the question how this genus achieved such a wide distribution. One possibility is that Armigatus originated in the Middle East and migrated toward America through the epicontinental marine environments. Another possibility is precisely the opposite, in which these fishes appeared in America and subsequently invaded the littoral environments to reach the Middle East. Since A. carrenoae is the oldest record of the genus, the second of these possibilities seems more plausible; however, the identification of the other Mexican species of Armigatus and the development of comprehensive phylogenetic and biogeographic studies may still significantly alter our understanding of the origin and dispersal of Armigatus .

Figures

FIGURE 1. Specimen IGM 11532, Armigatus brevissimus from the Cenomanian shallow marine deposits of Hekel, Lebanon, coated with magnesium smoke.

FIGURE 3. IGM 11536, holotype of Armigatus carrenoae sp. nov. from the Albian deposits of Tlayúa lagerstätte, near Tepexi de Rodríguez, Puebla, Mexico. A, photograph of the complete specimen under UV light. B, idealized drawing of the same specimen.

FIGURE 4. Paratypes of Armigatus carrenoae sp. nov. from Albian deposits of Tlayúa lagerstätte, near Tepexi de Rodríguez, Puebla, Mexico, photographed under UV light. A, IGM 11537. B, IGM 11538. C, IGM 11540.

FIGURE 5. Head of Armigatus carrenoae sp. nov. from the Albian deposits of Tlayúa lagerstätte, near Tepexi de Rodríguez, Puebla, Mexico. A, Closeup of IGM 11538, coated with magnesium smoke and photographed under white light. B, idealized and simplified drawing of A. Abbreviations: aa, anguloarticular; ao, antorbital; br, branchiostegal ray; cl, cleithrum; ddml depression for the dento-maxillar ligament; den, dentary; dsph, dermosphenotic; ect, ectopterygoid; ent, endopterygoid; epo, epioccipital; epn, epineurals; ext, extrascapular; fr, frontal; hm, hyomandibular; io, infraorbital; iop, interopercle; le, lateral ethmoid; mes, mesethmoid; mp, metapterygoid; mx, maxilla; na, nasal; naac, neural arches + spines of abdominal centrum; op, opercle; os, orbitosphenoid; os, orbitosphenoid; pa, parietal; pal, palatine; pcl, postcleithrum; pd, predorsal; pfr, pectoral fin ray; pop, preopercle; prvas, prepelvic abdominal scutes; psp, parasphenoid; pto, pterotic; pts, pterosphenoid; ptt, posttemporal; q, quadrate; r, rib; rar, retroarticular; sc, sclerotic; scl, supracleithrum; smx, supramaxilla; soc, supraoccipital; sop, subopercle; suo, supraorbital; dark arrow shows the basipterygoid process of the parasphenoid bone; (l) and (r) indicates the left and right side.

FIGURE 6. Part of the pectoral girdle, lower jaw, branchial arch, and branchiostegal rays of Armigatus carrenoae sp. nov. from the Albian deposits of the Tlayúa lagerstätte, near Tepexi de Rodríguez, Puebla, Mexico. A, closeup of the head of the paratype IGM 11537 under UV light. B, idealized and simplified drawing based on A. Abbreviations: aa, anguloarticular; ac, anterior ceratohyal; bh, basihyal; br, branchiostegal ray; cl, cleithrum; cor, coracoid; ddml depression for the dento-maxillar ligament; den, dentary; dh, dorsal hypohyal; iop, interopercle; pc, posterior ceratohyal; pcl, postcleithrum; pfr, pectoral fin ray; prvas, prepelvic abdominal scutes; q, quadrate; rar, retroarticular; rad, radial; sca, scapula; sop, subopercle; sy, symplectic; uh, urohyal; vh, ventral hypohyal.

FIGURE 7. Closeup of the postorbital region of IGM 11539 showing the osteoglossid-like tooth patch on the parasphenoid bone (black arrows). Abbreviations: hm, hyomandibular; mtp, metapterygoid; pop, preopercle; psp, parasphenoid.

FIGURE 8. Idealized and simplified drawing of the trunk and pelvic, anal, and dorsal fins of IGM 11536, holotype Armigatus carrenoae sp, nov. from the Albian deposits of Tlayúa lagerstätte, near Tepexi de Rodríguez, Puebla, Mexico (based on Figure 3). Abbreviations: afr, anal fin ray; afs, anal fin stay; appt, anal proximal pterygiophore; dfr, dorsal fin ray; dfs, dorsal fin stay; dppt, proximal pterygiophores of dorsal fin; epl, epipleural; epn, epineural; hapu, hemal arch and spine of preural centrum; naac, neural arch of abdominal centrum; napu, neural arch and spine of preural centrum; napu4, preural centrum 4 with double neural spine; pd, predorsal bone; php, parhypural; prvas, prepelvic abdominal scute; ptvas, postpelvic abdominal scute; pvfr, pelvic fin ray; r, rib; u, ural centrum; numbers under centra indicate their position along the vertebral column.

FIGURE 9. The caudal skeleton of Armigatus carrenoae sp. nov. from the Tlayúa Lagerstätte, near Tepexi de Rodríguez, Puebla, Mexico. A, closeup of the caudal skeleton of IGM 11538 coated with magnesium smoke. B, idealized and simplified drawing of A. Abbreviations: afr, anal fin ray; cs, caudal scute; ep, epural; epl, epipleural; epn, epineural; hapu, hemal arch of preural centrum; hy, hypural; napu, neural arch of preural centrum; nau, neural arch of ural centrum; php, parhypural; prl, branched and segmented caudal fin ray of the lower lobe; prlI, unbranched caudal principal fin ray of the lower lobe; pru, branched and segmented caudal fin ray of the upper lobe; pruI, unbranched caudal principal fin ray of the upper lobe; pu, preural centrum; u, ural centrum; un, uroneural.

FIGURE 10. Predorsal scutes series of A. carrenoae sp. nov. from Tlayúa. A, closeup of the predorsal region of IGM 11536 (inverted for comparative purposes). B, closeup of predorsal region of IGM 11537. C, idealized drawing of B. Abbreviations: afr, anal fin ray; pd, predorsal bone; pds, predorsal scutes; dppt, dorsal proximal pterygiophore; upds, unmodified predorsal scales.

FIGURE 12. Dorsal region of Armigatus brevissimus. A, closeup of the specimen IGM 11532 from the Cenomanian shallow marine deposits of Hekel, Lebanon, under white light. B, idealized and simplified drawing of predorsal scutes and near bones based on A. Abbreviations: afr, anal fin ray; pd, predorsal bone; pds, predorsal scutes; dppt, dorsal proximal pterygiophore; upds, unmodified predorsal scales.

FIGURE 13. Paleobiographical distribution and diversity of predorsal scutes of Armigatus. Abbreviations in the predorsal scute formula: C, complete predorsal scute series; I, incomplete predorsal scute series; the number of predorsal scutes in each species is shown in front of the draws; draws show the change in the shape of the scutes along the predorsal observed in species; light arrows point to posterior scutes; dark arrows show the hypothetic intraspecific change of the predorsal scutes.