Podocnemis aegyptiaca Andrews (1900)

PØrez-García, AdAEn, 2021, New shell information and new generic attributions for the Egyptian podocnemidid turtles “ Podocnemis ” fajumensis (Oligocene) and “ Podocnemis ” aegyptiaca (Miocene), Fossil Record 24 (2), pp. 247-262 : 254-256

Podocnemis aegyptiaca Andrews (1900) , DacquØ (1912), Fourteau (1920)

Erymnochelys aegyptiaca Williams (1954) , Broin (1977) aff. Erymnochelys aegyptiaca Lapparent de Broin (2000) “ Podocnemis ” aegyptiaca Gaffney et al. (2011) , PØrez-García et al. (2017), PØrez-García (2019), Lapparent de Broin et al. (2020)

Type material

Andrews (1900) figured a shell that he identified as the type specimen of this species (see Figs. 5a , 6a, d ; fig. 2C in plate 1 of Andrews, 1900), by drawings corresponding to the dorsal surface of the carapace, the ventral surface of the plastron and most of the xiphiplastral dorsal surface. This specimen is currently lost. An artificial mold of the type specimen is identified here, NHMUK R2927 ( Figs. 5b–c , 6b–c ), designated as the holoplastotype (see Evenhuis, 2008, and references therein).

Other specimens attributed to this taxon

Despite the fact that Andrews (1900) and Fourteau (1920) alluded to the presence of more specimens attributable to this species, from the type locality and area, only a second shell belonging to it has so far been analyzed and figured, by schematic drawings (see Figs. 4d , 6e ; fig. 21 of Fourteau, 1920). This specimen is currently lost. Some specimens found there in 1900 and deposited in the NHMUK are compatible with this species, being recognized here as cf. Apeshemys aegyptiaca : an almost complete third right costal, showing a sinuous margin of the third vertebral, compatible with the lateral rounded protrusion that characterizes the third vertebral of this species (see Diagnosis) ( NHMUK R2961; Fig. 7a–b ); a partial and articulated anterior plastral lobe, in which the medial contact of the extragulars is recognized, which represents an exclusive character for Erymnochelyini within Podocnemididae (see Discussion), this group being exclusively known by Apeshemys aegyptiaca in the early Miocene record ( NHMUK R2960; Fig. 7c– d ), and sharing with this species the presence of a narrow dorsal expansion of the pectoral scutes (see Diagnosis).

Diagnosis

Member of the lineage of Podocnemididae Erymnochelyini considering the medial contact of the extragulars, posteriorly to the reduced gular that they frame. It is defined by the following characters recognized as exclusive within this clade: second vertebral markedly wider than the third one; lateral rounded protrusions in the second and third vertebrals, anterior to the inter-pleural sulci. It shows the following unique combination of characters: absence of carapacial medial keel; six neurals; medial contact of the sixth to eighth pairs of costals; heptagonal first vertebral, with short latero-anterior margins, and wider than the nuchal; first pair of marginals overlapping on half of the nuchal lateral margins; absence of extragular protrusions; narrow dorsal expansion of the plastral scutes; anal length along the lateral xiphiplastral margin less than 2 times that of the femorals.

Figures

Figure 4. Plastral remains of the podocnemidid turtle Shetwemys fajumensis comb. nov. (Erymnochelyini), from the lower Oligocene (Rupelian) of the Fayum Depression (Fayum Governorate, northern Egypt). (a–b) NHMUK R3435, anterior plastral lobe, in ventral (a) and dorsal (b) views. (c–d) NHMUK R8441, plaster cast of the specimen CGM C8509, anterior plastral lobe, in ventral (c) and dorsal (d) views. (e–f) AMNH 5093, articulated epiplastra and entoplastron, in ventral (e) and dorsal (f) views. (g–h) SMNS 11233/6, anterior plastral lobe, in ventral (g) and dorsal (h) views. (i–j) NHMUK R3103, partial anterior plastral lobe, in ventral (i) and dorsal (j) views. (k–l) SMNS 11233/5, right hypoplastron, in ventral (k) and dorsal (l) views. (m–n) SMNS 11233/3, articulated left hypoplastron and xiphiplastron, in dorsal (m) and ventral (n) views, and detail of the outer ornamental pattern (o).

Figure 5. Carapace of the podocnemidid turtle Apeshemys aegyptiaca comb. nov. (Erymnochelyini), from the lower Miocene (Burdigalian) of the Qattara Depression (Matruh Governorate, northern Egypt). (a–c) Type specimen. (a) Drawing of the dorsal view of the carapace, corresponding to fig. 1 on plate 1 of Andrews (1900). (b–c) Carapace of the plaster cast NHMUK R2927, corresponding to the holoplastotype of the specimen, in dorsal (b) and ventral (c) views. (d) Dorsal view of a shell of another specimen, currently lost, based on fig. 21 of Fourteau (1920). It is important to point out that some details of this drawing were erroneous, such as the low number of peripherals.

Figure 6. Plastron of the podocnemidid turtle Apeshemys aegyptiaca comb. nov. (Erymnochelyini), from the lower Miocene (Burdigalian) of the Qattara Depression (Matruh Governorate, northern Egypt). (a–d) Type specimen. (a) Drawing of the ventral view of the plastron, corresponding to fig. 2 on plate 1 of Andrews (1900). (b–c) Plastron of the plaster cast NHMUK R2927, corresponding to the holoplastotype of the specimen, in ventral (b) and dorsal (c) views. (d) Drawing of the dorsal view of the posterior area of the posterior plastral lobe, corresponding to fig. 3 on plate 1 of Andrews (1900). (e) Ventral view of the partial plastron of another shell, currently lost, based on fig. 21 of Fourteau (1920).

Figure 7. Shell remains attributable to cf. Apeshemys aegyptiaca (Podocnemididae, Erymnochelyini), from the lower Miocene (Burdigalian) of the Qattara Depression (Matruh Governorate, northern Egypt). (a–b) NHMUK R2961, third right costal, in dorsal (a) and ventral (b) views. (c–d) NHMUK R2960, partial anterior plastral lobe, in ventral (c) and dorsal (d) views.