Profundulidae

The major node within Profundulidae 30.7–14.2 Mya (Fig. 3, node 5) separates Profundulus Hubbs, 1924 from Tlaloc Álvarez and Carranza, 1951 . Tlaloc occurs across the Chiapas Massif and adjacent highlands within the Río Grijalva drainage (Miller 1955, Cashner and Echelle 2020). The Upper Río Grijalva flows northwest until making an abrupt turn northeast, suggesting capture from a north-flowing river, possibly the ancestral Río Uxpanapa or Tonalá. This capture could have been caused by uplift of the northwestern Chiapas Massif 30–25 Mya (Witt et al. 2012) or head-cutting of the lower Río Grijalva during a period of extensive erosion 35–25 Mya (Abdullin et al. 2016) and potentially explains the distinctiveness of the Upper Grijalva fish community (Elías et al. 2020). Divergence of Tlaloc from Profundulus, which probably arose in an ancestral Río Coatzacoalcos (Fig. 8), provides an estimate for timing of this capture (Table 2).

Notably, Profundulus is now largely restricted to Pacific slope drainages (Domínguez-Cisneros et al. 2023). Presuming that Miocene, upland Profundulus no longer tolerated high-salinity or coastal environments, rising sea levels could explain the rarity of Profundulus on the Gulf slope, as proposed for Herichthys Baird & Girard, 1854 (Pérez-Miranda et al. 2020). During the Middle Miocene Climatic Optimum (MMCO) 17.0–13.8 Mya (Miller et al. 2020b), seas inundated broad areas north and east of the Sierra Madre del Sur and Chiapas Massif (Blakey and Ranney 2018). Our chronogram indicates that diversification within Profundulus occurred thereafter (Fig. 3), potentially from one refugial population.