Reptilia · Testudines
Phrynops williamsiRhodin & Mittermeier, 1983
William’s Toadhead Turtle
Photograph by Mark Bolnik, CC BY, via iNaturalist
A day-active turtle from the Neotropic region, reaching 355 mm nose to tail.
Also called William’s South-American Side-necked Turtle.
Reptilia › Testudines › Chelidae › Phrynops
- Grows to
- 355mm
- greatest recorded
- Active
- Diurnal
- Lives
- Aquatic, terrestrial
- Weighs up to
- 4540g
- greatest
Longer than 83% of all species in Chelidae anyone has measured.
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
18 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
- Vulnerable
- Population trend
- Decreasing
The animal itself
- Pupil
- Round
- Venomous
- No
- Fangs
- None
Size
- Length nose to tail · greatest recorded
- 355mm14 in
- Body mass · greatestcomputed
- 4540g10 lb
total length, tail included — Colston, Kulkarni, Jetz, and Pyron, 2020, BMC Evol. Biol., 20:81
largely converted from length by allometry in the source
How it lives
- Active
- Diurnal
- Where it lives
- Aquatic, terrestrial
- Habitat
- Wetlands
- Region
- Neotropic
- Elevation · above sea level
- 80–100m
Breeding
- Reproduction
- Oviparous
- Average clutch
- 9eggs
Naming and history
- Subspecies
- No
- Described by
- Rhodin & Mittermeier
- Moved to another genus · since it was first described
- No
- Described in
- 1983
Feeding
349kJ per day
Worked out for an animal of 4,540 g, the heaviest recorded for William’s Toadhead 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
- — Shell length, front to back · greatest recorded
- — 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
- — Egg length
- — Egg width
- — Body mass · a typical adult
- — Body mass · adult female, mean
- — Body mass at hatching
- — Longest recorded life
- — Preferred body temperature · chosen in a laboratory gradient
- — Body temperature when active · measured in the wild
- — Diet
- — Eats arthropods
- — Eats vertebrates
- — Eats plant matter
- — How it hunts
- — How the young develop
- — Gestation or incubation
- — Smallest clutch recorded
- — Largest clutch recorded
- — 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
- — Colour on the back
- — Pattern on the back
- — 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
- — Range size
Others in Chelidae
- (Western) Twist-neck Turtle
- Amazon Mata Mata
- Arnhem Land Long-Necked turtle
- Bells’ Turtle
- Big-headed Pantanal Swamp Turtle
- Black Spine-necked Swamp Turtle
- Black-lined Toadhead Turtle
- Brasilianische Krötenkopfschildkröte
- Brazilian Radiolated Swamp Turtle
- Cann's Snake-necked Turtle
- Chaco Side-necked Turtle
- Common Snake-necked Turtle
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). Phrynops williamsi. Retrieved 2026-09-08, from https://www.allanglescreatures.com/species/phrynops-williamsi
@misc{phrynops_williamsi_2026,
title = {Phrynops williamsi},
author = {{The Reptile & Amphibian Encyclopedia}},
year = {2026},
url = {https://www.allanglescreatures.com/species/phrynops-williamsi}
}Sources
- 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.
- Oskyrko, O. et al. (2024). ReptTraits: a comprehensive dataset of ecological traits in reptiles. Scientific Data. Used under CC BY 4.0.
- Catalogue of Life (dataset 3LR), used under CC BY.