This taxon was originally assigned by Mertens (1954) to the genus Geoemyda, and described as a subspecies of G. punctularia (as G. p. diademata) but later reassigned to Callopsis by Smith et al. (1974). Pritchard (1979) elevated it to full species and transferred it to the genus Rhinoclemmys. Although initially some authors did not recognize its status as a species (e.g., Ernst 1981, Paolillo 1985) this is currently not questioned (TTWG 2021). Most phylogenetic hypotheses have recovered R. diademata as the sister species of R. punctularia and both in turn as sisters to a clade containing R. melanosterna and R. funerea (e.g., Carr 1991, Spinks et al. 2004, Le and McCord 2008, Thomson et al. 2021). Although Vargas-Ramírez et al. (2013) recovered contradictory relationships for these four species between their mitochondrial and nuclear phylogenies, they argued that their results suggested past gene flow among the species.

Rhinoclemmys diademata is assessed as Endangered (EN) under criteria A2cde+4cde because it is suspected that its populations have suffered a reduction of around 50% over the last three generations (c. 50 years) as well as over the last two generations (c. 34 years) and projected to continue for at least one generation (c. 17 years) into the future, due to overexploitation of individuals for subsistence consumption, the reduction and degradation of its habitat, and the impact of introduced taxa that represent ecological competitors. The causes of this reduction have not ceased, are not well understood, and may not be reversible. Rhinoclemmys diademata was previously assessed as Least Concern (LC) in 1996 by the IUCN Tortoise and Freshwater Turtle Specialist Group (TFTSG) (Behler 1996) and consequently was not included on the Red List at that time; it was provisionally assessed as Vulnerable (VU) in 2011 by the TFTSG (Rhodin et al. 2018).

Rhinoclemmys diademata has one of the smaller distribution ranges among South American turtle species. It is endemic to the Maracaibo Lake basin (Pritchard and Trebbau 1984, Armesto et al. 2014, TTWG 2021). In Colombia, it is distributed in the Catatumbo River basin, Norte de Santander department, in the municipalities of Cúcuta (Armesto et al. 2011), Sardinata, Zulia, and Tibú (Ceballos-Fonseca 2000, Castaño-Mora 2002). The Catatumbo River runs partly in Colombia and partly in Venezuela, flowing into Lake Maracaibo. In Venezuela, R. diademata is known from the northwest, west, south, and southeast of the Lake Maracaibo basin, from the margins of the estuary to the foothills of the Serranía de Perijá in the west and Cordillera de Mérida in the east, in the states of Mérida, Táchira, Trujillo, and Zulia (Pritchard and Trebbau 1984, Rivas et al. 2015). The species has been recorded from near sea level to 330 m asl. The estimated historical indigenous range (area of occupancy, AOO) was approximately 45,457 km², and the estimated historical indigenous extent of occurrence (EOO) was approximately 64,861 km² (TTWG, in press); however, the current AOO is significantly smaller than its estimated historical range.

There are no published studies that systematically assess the population sizes or local abundances of this species; however, the species has in the past been considered common throughout most of its range. There is an historical anecdotal record of between 200–300 specimens collected in Tulé dam between 1970–1971 (J. Lira pers. comm. in Pritchard and Trebbau 1984). More recently, García and Péfaur (2011) stated that Rhinoclemmys diademata was one of the more abundant turtles in the southern region of the Lake Maracaibo basin during their samplings of 2008–2009. In addition, it is still fairly common to find tens of captive specimens in homes in rural areas of the region, representing individuals found by chance and collected for subsistence consumption (F.J.M. Rojas-Runjaic pers. obs.). However, overall, populations do not currently appear to be as abundant as in the past.

Information regarding the ecology of Rhinoclemmys diademata is limited to a few specific observations. It is semi-aquatic and active in daytime, inhabiting lentic and lotic water bodies without significant currents, such as lagoons, ponds, or canals in the areas of pools and wells (Pritchard and Trebbau 1984, Castaño-Mora 2002). It is frequently found walking overland or crossing roads, far from bodies of water (Pritchard and Trebbau 1984, Castaño-Mora 2002). The waters it inhabits are generally clear, of Andean origin (fertile), and the associated ecosystems are humid basal forest and humid basal shrubland in the southern Maracaibo basin (Morales-Betancourt et al. 2017), and dry forest in the northwestern portion of the basin (F.J.M. Rojas-Runjaic pers. obs.). The species seems to be omnivorous, although some authors have suggested that it is herbivorous (Armesto et al. 2014), or carnivorous (Castaño-Mora 2002). It feeds on aquatic plants, insects, snails, worms and other small invertebrates, both on land and in water (Pritchard and Trebbau 1984).

Courtship and mating take place both on land or in water. Nesting occurs throughout the year, apparently at intervals of ca. two months. Clutches consist of 1–3 large, brittle-shelled eggs, which are laid directly on the ground or semi-buried and covered with plant material; annual fecundity in captivity is between 6–18 eggs per year (Fuchs 2016). Eggs are 4.3–7.1 cm long and 2.6–3.5 cm wide (Pritchard and Trebbau 1984, Fuchs 2016). Females do not nest in seasons of food scarcity or in very dry years. There are no data on size at sexual maturity; only one observation of courtship and mating activity has been made in captivity by a male individual with a straightline carapace length (SCL) of 13.3 cm. The maximum adult SCL reported is 18.7 cm in males and 28.5 cm in females; neonates measure 4.2–6.3 cm (Pritchard and Trebbau 1984; Rivas et al. 2007, 2015; Fuchs 2016). Generation time for R. diademata is not known, but is estimated to be between 10–17 years based on congenerics and Iverson (2024). Longevity is estimated to exceed 50 years based on a captive R. melanosterna reported by Iverson (2014), and still alive in 2024 (Iverson, unpubl. data).

Rhinoclemmys diademata is traditionally is used for subsistence consumption throughout its range. It is especially collected during Holy Week, but is not restricted to that time, and harvests may be particularly intense, as illustrated by the anecdotal record of 200–300 specimens collected in Tulé dam between 1970–1971, which were consumed locally (J. Lira pers. comm. in Pritchard and Trebbau 1984). Although not quantified, it is presumed that, as with other wild animals, capture of specimens of R. diademata for consumption has increased dramatically in recent years to compensate for the deficit of animal protein in homes as a consequence of the economic crisis suffered in Venezuela (Gutiérrez 2018). Being a species with a restricted distribution and a low reproductive rate, the overexploitation of juveniles and adults of R. diademata for subsistence consumption can substantially affect its populations (Rivas et al. 2008, 2015).

Additionally, the ecosystems where the species is distributed are highly affected. In Colombia, the area of distribution has been strongly transformed into rice agroecosystems and mosaic grasslands and crops (Morales-Betancourt et al. 2017) and further impacted by illicit crops, coal mining, oil, and poor water quality (Morales-Betancourt et al. 2012). In Maracaibo basin there are numerous canals built for irrigation; it is unclear whether these have harmed the species or if, on the contrary, they may have benefited it, by providing a greater availability of potential habitat (Morales-Betancourt and Lasso 2015). In Venezuela, there is also a significant loss of habitat as a result of agricultural, livestock, fish farming, and mining development (Rivas et al. 2008, 2015). The habitats of this species are considered Endangered (Maracaibo dry forests) and Critically Endangered (Catatumbo humid forests) (Llamozas et al. 2003, Oliveira-Miranda et al. 2010). The apparently recent introduction (or distribution expansion?) of Trachemys callirostris callirostris into the southern region of the Lake Maracaibo basin (F.J.M. Rojas-Runjaic per. obs. 2006, García and Péfaur 2011) could represent an additional threat to R. diademata, since T. c. callirostris is a more prolific and aggressive species than R. diademata and likely a more successful ecological competitor.

In Venezuela and Colombia the use of Rhinoclemmys diademata is local, as adults and juveniles are used for meat and subsistence consumption (Pritchard and Trebbau 1984, Rivas et al. 2007, Morales-Betancourt and Lasso 2012). The species is also used as a pet in Cúcuta and El Zulia, Norte de Santander, Colombia (Armesto et al. 2014).

There have been no specific conservation measures or proposals implemented for R. diademata. In Colombia, it is classified as Endangered B1ab(iii) since it has a very restricted distribution, with an area of presence of less than 5,000 km² (1,465 km², Forero-Medina et al. 2014) and less than five localities (from two to five) and their threats have not yet been controlled or mitigated (habitat quality) (Morales-Betancourt and Lasso 2015). Part of its distribution overlaps with the Catatumbo-Bari Natural Park protected area (Castaño-Mora 2002). It is protected by the National Program for the Conservation of Marine and Continental Turtles in Colombia (MMA 2002). In Venezuela it is classified as Endangered B2ab(iii,v), given the estimated area of occupancy of less than 500 km², which is severely fragmented or the species is known from no more than five locations. There is a continued, observed, inferred or projected decline in range area and/or habitat quality and in the number of mature individuals. It is partly covered by the protective figure of five Areas Under Special Administration Regime (ABRAE): Protection Zone of the City of Maracaibo (20,800 ha), Ciénegas de Catatumbo National Park (269,000 ha), Lago de Maracaibo Region Protection Zone, Polygons 1 and 2 (Sierra de Perijá; 244,125 ha), Zona Sur del Lago de Maracaibo Hydraulic Reserve (618,000 ha), and Ciénegas de Juan Manuel de Aguas Blancas y Aguas Negras Wildlife Reserve (71,500 ha) (Rivas et al. 2008, 2015). In addition, it is protected in Venezuela by the Ley de Protección a la Fauna Silvestre (G.O. 29289; 11 August 1970).

The species was listed in CITES Appendix II as Rhinoclemmys sp. as of 2023. Being a species restricted to a basin shared between Colombia and Venezuela, it is necessary to reach binational agreements for its conservation. Studies of its natural history and demography are needed to more accurately evaluate its population status, as well as evaluate threats across its distribution. Furthermore, because R. diademata is a thermo-dependent species, it is necessary to carry out studies that allow for modelling of the possible influence of climate and environmental changes on the survival of the species (Morales-Betancourt and Lasso 2015).

Rhinoclemmys diademata was assessed as Least Concern (LC) in 1996 by the IUCN Tortoise and Freshwater Turtle Specialist Group (TFTSG) (Behler 1996) and consequently was not included on the Red List at that time; it was provisionally assessed as Vulnerable (VU) in 2011 by the TFTSG (Rhodin et al. 2018, TTWG 2021).