All Angles Creatures
Testudines · ChelidaeEntry 78 of 21,572
Big-headed Pantanal Swamp Turtle, Acanthochelys macrocephala

Reptilia · Testudines

Acanthochelys macrocephalaRhodin, Mittermeier, Mcmorris, 1984

Big-headed Pantanal Swamp Turtle

Photograph by Adrien Jailloux, CC BY, via iNaturalist

A nocturnal, meat-eating turtle from the Neotropic region, reaching 24 cm across the shell.

Reptilia › Testudines › Chelidae › Acanthochelys

Grows to
295mm
greatest recorded
Eats
Carnivorous
Active
Nocturnal
Lives
Aquatic, terrestrial
Body length across Chelidae

Longer than 60% of all species in Chelidae anyone has measured.

60% of 42 species are smaller40% larger
155 mmthe whole family, smallest to largest500 mm

The bar is the rank itself: its length is the share of the family this animal exceeds. The chart below is the family’s real spread, on a logarithmic scale because body length here runs from 155 to 500 mm. The solid rule is this animal. Every bar is a count of real species, and nothing on this figure is estimated.

What is known

26 sourced facts, each taken from a named scientific dataset. How to read these.

Cited from a dataset unless a row is marked otherwise.

Standing in the world

Conservation status
Near Threatened
Population trend
Decreasing

The animal itself

Colour on the back
Black, Brown
Pattern on the back
Uniform
Pupil
Round
Venomous
No
Fangs
None

Size

Length nose to tail · greatest recorded
295mm11.5 in

total length, tail included — Colston, Kulkarni, Jetz, and Pyron, 2020, BMC Evol. Biol., 20:81

Shell length, front to back · greatest recorded
235mm9.25 in

straight carapace length, measured in a line rather than over the curve

Body mass · greatestcomputed
2895g6.4 lb

largely converted from length by allometry in the source

Body mass at hatching
20g0.71 oz

How it lives

Diet
Carnivorous

Invertebrates

Active
Nocturnal
Where it lives
Aquatic, terrestrial
Habitat
Wetlands
Region
Neotropic
Highest it lives · above sea level
500m

Breeding

Reproduction
Oviparous
Average clutch
6eggs
Eggs or young per clutch
4–8eggs
Egg length
31mm1.25 in
Egg width
32.5mm1.25 in

Naming and history

Subspecies
No
Described by
Rhodin, Mittermeier, Mcmorris
Moved to another genus · since it was first described
Yes
Described in
1984

Keeping one

3 ft 1 in × 18.5 in(94 × 47 cm)

Minimum floor length × width, for one animal. Bigger is always better. The standard sets no height for turtles and tortoises.

The standard sizes this genus at 4 times carapace length, with the width half the resulting length.

For a third and fourth turtle the standard asks for at least 10% more floor area each, and 20% more from the fifth onwards.

Water depth is set against the animal's carapace width rather than its length, so no figure is given here. Dry-country tortoises need no water area, only occasional bathing; tortoises from wetter regions need a water dish.

Swiss law reaches the same 8 × 4 of carapace length for land tortoises, arrived at separately from the German gutachten.

Gutachten über Mindestanforderungen an die Haltung von Reptilien (Sachverständigengruppe tierschutzgerechte Haltung von Terrarientieren), German Federal Ministry, 10 January 1997, section 5. The standard states these are recommendations rather than binding limits.

Swiss Tierschutzverordnung (TSchV), SR 455.1, Anhang 2, Tabelle 5 — legally binding minimum enclosure sizes, which give every land tortoise 8 × 4 body lengths for two animals.

From this animal’s own carapace length of 9.25 in (235 mm), at 4 times it — how this is worked out.

No preferred body temperature has been recorded for Big-headed Pantanal Swamp Turtle. Rather than repeat a number from a care sheet, this page leaves it out.

Feeding

A prey item should be no wider than the space between the animal's eyes.

Widely used across reptile husbandry references. The stated reason is that the gap approximates the width of the throat, so wider prey is associated with impaction. This is established practice, not a measurement.

234kJ per day

Worked out for an animal of 2,895 g, the heaviest recorded for Big-headed Pantanal Swamp Turtle — so it is the top of the range, not a figure for a particular animal. Weigh yours and the number will be lower.

An upper estimate, not a feeding target, and not veterinary advice. The equation covers only what an animal burns staying alive, so a growing, gravid or recovering animal needs more — and it was measured on wild animals, which move far more than one in an enclosure. Body condition and a vet who knows the species are what a feeding decision should rest on. Where this comes from.

What nobody knows

These are not gaps in our research. No scientific dataset records them for this species — and saying so is information you cannot get from a reference that simply leaves a field out.

  • — Still living
  • — Length snout to vent · greatest recorded
  • — Length snout to vent · adult female mean
  • — Length snout to vent · adult male mean
  • — Length snout to vent · adult mean
  • — Female length · mean, nose to tail
  • — Length nose to tail · adult male mean
  • — Length nose to tail · adult mean
  • — Largest female · snout to vent
  • — Largest male · snout to vent
  • — Largest female · shell length
  • — Largest male · shell length
  • — Hatchling length · snout to vent
  • — Hatchling length · nose to tail
  • — Largest juvenile · snout to vent
  • — Largest juvenile · shell length
  • — Body mass · a typical adult
  • — Body mass · adult female, mean
  • — Longest recorded life
  • — Preferred body temperature · chosen in a laboratory gradient
  • — Body temperature when active · measured in the wild
  • — Eats arthropods
  • — Eats vertebrates
  • — Eats plant matter
  • — How it hunts
  • — How the young develop
  • — Gestation or incubation
  • — Mean clutch · smallest reported
  • — Mean clutch · largest reported
  • — Clutches in a year
  • — Clutches a year · fewest
  • — Clutches a year · most
  • — First breeds from · youngest recorded
  • — First breeds by · oldest recorded
  • — Hatchling length · smallest recorded
  • — Hatchling length · largest recorded
  • — Age at first breeding · female
  • — Mature from · youngest recorded
  • — Mature by · oldest recorded
  • — Size at maturity · smallest recorded
  • — Size at maturity · largest recorded
  • — Body temp in the wild · lowest mean recorded
  • — Body temp in the wild · highest mean recorded
  • — Limbs
  • — Sex decided by
  • — Status assessed · the year the Red List last looked
  • — Red List criteria
  • — Biome
  • — Active season · shortest recorded
  • — Active season · longest recorded
  • — Density · lowest recorded
  • — Density · highest recorded
  • — Home range · largest recorded
  • — Suborder
  • — Infraorder
  • — Type locality
  • — Active in
  • — Mainland or island
  • — Lowest it lives · above sea level
  • — Range size

Others in Chelidae

Take this data

Everything on this page is available as data under CC BY 4.0 — use it freely, credit it, no permission needed.

This species as JSON · the whole dataset

Cite this page

The Reptile & Amphibian Encyclopedia (2026). Acanthochelys macrocephala. Retrieved 2026-09-08, from https://www.allanglescreatures.com/species/acanthochelys-macrocephala

@misc{acanthochelys_macrocephala_2026,
  title  = {Acanthochelys macrocephala},
  author = {{The Reptile & Amphibian Encyclopedia}},
  year   = {2026},
  url    = {https://www.allanglescreatures.com/species/acanthochelys-macrocephala}
}

Sources

  1. Moura, M. R. et al. TetrapodTraits: a database of 33,281 tetrapod species. Used under CC BY 4.0. Observed values only; this encyclopedia does not publish its imputed predictions.
  2. Oskyrko, O. et al. (2024). ReptTraits: a comprehensive dataset of ecological traits in reptiles. Scientific Data. Used under CC BY 4.0.
  3. Catalogue of Life (dataset 3LR), used under CC BY.