10 Reptiles That Are the Only Living Species in Their Families

Cover image: Wikimedia Commons — Tuatara

A leatherback turtle crosses the open ocean. A tuatara rests beside a burrow on a New Zealand island. They look very different, yet they share something surprising: each is the only living species in its family.

Here, “family” means a group in biological classification—not parents and offspring. Some reptile families contain hundreds of living species. The families featured here contain just one.

That does not necessarily mean these animals are rare in the wild. It tells us how they are classified, not how many individuals remain.

Our ten reptiles include a freshwater turtle with flippers, a legless reptile that digs with its head, and a tiny snake that remained hidden from scientific view for about a century. Their names give us a starting point. Their shells, snouts and teeth offer plenty to discover along the way.

What Does “One Living Species in a Family” Mean?

Biologists organise living things into groups that help describe their relationships. For this article, we need three levels, moving from a broader group to a narrower one:

Family → Genus → Species

A family contains one or more genera—the plural of “genus”. A genus contains one or more species.

The leatherback turtle provides a straightforward example:

Level	Name	Living members
Family	Dermochelyidae	One genus: Dermochelys
Genus	Dermochelys	One species: Dermochelys coriacea
Species	Dermochelys coriacea	The leatherback turtle

Each reptile in this article follows that pattern: its family contains one living genus, and that genus contains one living species. Fossil species and species that have already become extinct are not included in this count.

You may also encounter the word monotypic, which describes a taxonomic group containing only one immediately subordinate group. The important point here is the full arrangement: one living genus containing one living species.

Two distinctions are worth keeping in mind.

First, “one species” counts kinds of animals, not individuals. A species can have many individuals across a wide area while remaining the only living representative of its family.

Second, having no other living species in the same family does not mean having no relatives. Follow the evolutionary tree further back, and these animals share ancestors with members of other families.

Meet the Ten Reptiles

This selection follows the classification adopted for this article, principally based on The Reptile Database, with a classification reference date of 21 October 2026. The database brings together scientific names, classification, distribution records and references for living reptiles. As research changes species boundaries, a list like this can change too.

Scientific names have two parts: the genus name comes first, followed by the specific epithet. Together, they identify the species. There is no need to memorise them before we begin; you can return to this table as we meet the animals.

Common name	Scientific name	Family	Main distribution
Leatherback turtle	Dermochelys coriacea	Dermochelyidae	Oceans worldwide
Pig-nosed turtle	Carettochelys insculpta	Carettochelyidae	Southern New Guinea and northern Australia
Central American river turtle	Dermatemys mawii	Dermatemydidae	Southern Mexico, Belize and Guatemala
Chinese crocodile lizard	Shinisaurus crocodilurus	Shinisauridae	Southern China and northern Vietnam
Earless monitor lizard	Lanthanotus borneensis	Lanthanotidae	Borneo
Florida worm lizard	Rhineura floridana	Rhineuridae	Florida and Georgia, USA
Red pipe snake	Anilius scytale	Aniliidae	Northern South America, including Amazonia
Mexican burrowing python	Loxocemus bicolor	Loxocemidae	Mexico to Costa Rica
Madagascar blind snake	Xenotyphlops grandidieri	Xenotyphlopidae	Northern Madagascar
Tuatara	Sphenodon punctatus	Sphenodontidae	New Zealand

These are ten examples under the classification followed here, rather than a list that will remain unchanged forever. Later, we will meet a turtle that no longer qualifies—and see why a change in classification can tell an interesting story.

Three Turtles: Different Ways to Live in Water

Our first three reptiles are turtles. One travels through the open ocean; the other two inhabit fresh water.

Their shells and front limbs provide an easy way into their lives. Their food then leads us further, connecting jellyfish in the sea with leaves falling from riverside trees.

1. Leatherback Turtle: A Shell Covered in Skin

• Family: Dermochelyidae
• Main range: Oceans worldwide, from tropical waters to colder seas at high latitudes

The leatherback is the largest living turtle. Its shell also has a distinctive surface.

Most familiar turtles have shells covered in hard, keratinous plates called scutes. Keratin is also the material that forms our fingernails. The leatherback lacks this covering of hard scutes. Instead, tough skin covers a mosaic of small bones, and seven ridges run lengthways down its back.

Long front flippers propel it through the water. It travels great distances between nesting beaches in warm regions and feeding grounds that may lie in much colder seas.

Its food includes jellyfish and salps. Salps are transparent, barrel-shaped animals that drift in the sea. Although they may look rather jellyfish-like, they are relatives of sea squirts.

Inside the leatherback’s mouth and throat, backward-pointing projections help retain slippery, soft-bodied prey.

A whole-body photograph shows the swimming equipment: long flippers and a streamlined body. A photograph of the mouth reveals another part of the same life—the structures that help it hold its food.

When comparing the leatherback with another sea turtle, such as a loggerhead, begin with the shell surface. The contrast between skin and hard scutes is easier to remember once you have noticed it yourself.

2. Pig-nosed Turtle: Flippers in Fresh Water

• Family: Carettochelyidae
• Main range: Southern New Guinea and northern Australia

Look at a pig-nosed turtle from the front, and its name needs very little explanation. A fleshy, rounded snout projects from the head, with the nostrils at its tip.

Its front limbs offer another surprise. They are broad and flipper-like, resembling those of a sea turtle, although this species lives in fresh water.

The turtle moves its front flippers together as it swims. Look closely at their tips, and you can see two claws on each.

Its diet includes both animal and plant food: molluscs, crustaceans, leaves, fruit and seeds. However, its strong connection to water does not remove its need for land. Females come ashore to dig nests and lay eggs on riverbanks.

The habitat therefore includes more than the river itself. Suitable banks are where the next generation begins.

3. Central American River Turtle: A Meal from the Riverbank

• Family: Dermatemydidae
• Main range: Atlantic-draining rivers and lakes of southern Mexico, Belize and Guatemala

The Central American river turtle, also known as the hickatee, is a large freshwater turtle. It is the only living species in Dermatemydidae and is strongly associated with rivers and lakes.

Adults feed mainly on plants. But does an aquatic turtle necessarily eat plants that grow underwater?

A 2022 study by Bishop and colleagues provides a useful answer. The researchers examined the stomach contents of 66 turtles legally harvested for local consumption in Belize. They found leaves, flowers, stems, seeds and fruit, among other plant material. Diet differed between river and lagoon habitats, and leaves from riverside trees were especially important in rivers.

An animal beneath the surface can therefore depend on plants growing above it.

When looking at a river, we might separate the water from the wooded bank. The turtle’s meals connect them: a leaf falls, sinks or drifts, and becomes food.

Lizards and a Worm Lizard: From Streamside Branches to Soil

Our next three reptiles lead us from forest streams into the ground.

Their shapes can be misleading at first. A crocodile-like tail does not make an animal a crocodile, and a long, legless body does not automatically make it a snake.

Looking at where an animal rests—and how it moves—helps make sense of its appearance.

4. Chinese Crocodile Lizard: A Perch Above the Water

• Family: Shinisauridae
• Main range: Southern China and northern Vietnam

The Chinese crocodile lizard lives around slow-moving streams and pools in forest.

Its name draws attention to its crocodile-like appearance, particularly the tail. But the branch beneath its feet tells us something equally useful.

A branch overhanging water is more than a resting place. If danger approaches, the lizard can drop into the stream and hide underwater.

The water is also a place to find food. Its prey includes insects, earthworms, snails and tadpoles.

Imagine the habitat in three dimensions: branches above, banks beside, and water below. The lizard uses the connections between them.

That helps explain why the surrounding forest matters. Losing it removes perches and shelter, while capture for the pet trade puts additional pressure on the species. Protecting the lizard means protecting the wooded stream as a whole.

5. Earless Monitor Lizard: Looking Beneath the Scales

• Family: Lanthanotidae
• Main range: Borneo

The earless monitor lizard has an elongated brown body, short legs and rows of raised, knobbly scales.

Its name refers to the absence of external ear openings. In a photograph, the textured skin may attract your attention first, followed by the small limbs and long body.

Much of its life takes place concealed in soil or water, making its behaviour difficult to follow in the wild. Field studies are gradually adding to our understanding of its activities.

Researchers can also investigate what lies beneath the scales.

The University of Texas at Austin’s DigiMorph resource provides images of the skull reconstructed from CT scans. CT scanning uses X-rays to reveal internal structures, allowing researchers to examine bones while leaving the specimen intact.

An external photograph and a reconstructed skull offer two views of the same head. One shows the surface encountered by the outside world; the other reveals the framework beneath it.

For a museum specimen, that distinction matters. Preserving the whole animal can leave several kinds of evidence available for future study.

6. Florida Worm Lizard: A Head Built for Digging

• Family: Rhineuridae
• Main range: Florida and Georgia, USA

The Florida worm lizard lives beneath the soil. Its long, legless body may bring an earthworm or a snake to mind.

It is neither. It belongs to the amphisbaenians, commonly called worm lizards—a group of reptiles distinct from snakes.

The head is the feature to examine. Its broad, shovel-like front helps push through soil, opening a route for the body behind it.

We often associate digging with limbs and claws. Here, the front of the head does the work.

The Florida worm lizard is the only living species in Rhineuridae and the only amphisbaenian native to the United States. Yet one species does not mean that every population is identical.

By comparing genetic information with records of where animals were found, researchers can investigate relationships between populations. Even for a reptile hidden underground, a precise locality record helps place an individual within a wider story.

Three Snakes: Clues Near and Below the Ground

Worm lizards are not snakes. Our next three reptiles, however, are.

They range from a brightly banded species to a pale, worm-like burrower. To learn about them, researchers draw on observations of living animals, preserved specimens and the records that accompany them.

7. Red Pipe Snake: A Specimen’s Last Meal

• Family: Aniliidae
• Main range: Northern South America, including the Amazon region

The red pipe snake has striking red and black bands. It spends much of its life concealed, and large individuals can approach 1.2 metres in total length.

Females give birth to live young rather than laying eggs.

Its food often has something in common with the snake itself: a long, narrow body. Prey includes worm lizards, other snakes and caecilians. Caecilians are limbless amphibians—not snakes, despite the similar outline.

A study published by Maschio and colleagues in 2010 investigated the diet of red pipe snakes from Brazilian Amazonia by examining preserved specimens. Remains inside the digestive tract provided evidence of their meals.

A researcher does not always have to witness a feeding event to learn from it. A specimen may preserve both the predator and traces of its prey.

In the field, observe snakes from a distance. Red and black colouring alone is not a reliable guide to whether a snake is venomous.

8. Mexican Burrowing Python: A Familiar Name, a Different Family

• Family: Loxocemidae
• Main range: Mexico and parts of Central America, south to Costa Rica

The Mexican burrowing python’s name seems to tell us where to place it. Surely a python belongs in the python family?

In this case, the common name and the family name do not line up. This snake belongs to Loxocemidae, not Pythonidae.

Common names are useful introductions, but they do not always provide a precise guide to classification.

Look at the head from the side. The snout projects forwards, with a sloping front that looks almost as though it has been cut off at an angle.

This species lays eggs, unlike the live-bearing red pipe snake.

Both are the only living species in their families, but that shared feature tells us neither what their heads look like nor how they reproduce. It gives us a reason to compare them—not a reason to expect them to be alike.

9. Madagascar Blind Snake: A Rediscovery Beneath the Sand

• Family: Xenotyphlopidae
• Main range: Coastal northern Madagascar, around Antsiranana

Pale pink and slender, the Madagascar blind snake looks remarkably like an earthworm.

At the front of its small head is an enlarged scale that helps it push through sand. Its body is suited to a life largely hidden from view—which also makes it difficult for people to find.

Its scientific history shows how incomplete records can add to that difficulty.

The species was described in 1905, but the old specimens were labelled only “Madagascar”. That left later researchers with a very large island to search.

Roughly a century later, snakes collected in the northern coastal region provided much more precise places to investigate. Comparisons with older specimens helped researchers understand the identity and distribution of the newly found animals.

A long gap without a record is not, by itself, proof that a species has become extinct. It may also reflect a concealed way of life, limited searching or uncertainty about where to look.

The rediscovery also demonstrates the value of a specimen label. “Madagascar” and a carefully recorded collecting site are very different kinds of information.

10. Tuatara: A Different Branch from Lizards

• Family: Sphenodontidae
• Main range: New Zealand, including offshore islands and protected conservation sites

At first glance, a tuatara looks like a lizard. Its classification reveals a deeper distinction.

Lizards and snakes belong to the order Squamata. An order is a broader classification level above family. The tuatara belongs to a different order, Rhynchocephalia, also called Sphenodontia in some accounts.

It is therefore unusual at more than one level: it is the only living species not just in its family, but in its entire order. New Zealand’s Department of Conservation recognises the tuatara as a single living species, Sphenodon punctatus.

The teeth provide a memorable clue to its anatomy. There are two rows in the upper jaw and one in the lower jaw. When the mouth closes, the lower teeth fit between the upper rows.

Its food includes beetles, spiders and other small animals. It sometimes eats lizards, seabird eggs and chicks.

Yet its relationship with seabirds extends beyond predator and prey. Seabirds bring nutrients from the sea onto their nesting islands. Those nutrients enrich the soil and help support the small animals that tuatara eat. An animal resting beside a burrow is therefore connected to food webs extending into the surrounding ocean.

The tuatara also gives us an opportunity to explore something that affects this whole article: classification can change.

Why the Big-headed Turtle Is Missing

The big-headed turtle previously appeared on ECO LIFE PLANET as the only living species in its family.

Under the classification followed here, it no longer qualifies.

A 2025 study by Liang and colleagues compared genetic evidence and physical characteristics across big-headed turtle populations. The researchers recognised three species where one had previously been widely recognised.

Scientific name	Treatment in the revision
Platysternon megacephalum	Retained with a narrower species definition
Platysternon peguense	Recognised as a separate species
Platysternon baiseensis	Described as a new species

The study found deeply divergent lineages and described Platysternon baiseensis from the Baise–Hechi region of Guangxi, China. Under this treatment, Platysternidae contains more than one living species.

The turtles did not suddenly change in 2025. Nor did a new species come into existence when its description was published.

The differences were already there. Research changed how scientists interpreted them: variation once placed within a single species was recognised as evidence of separate species.

Tuatara Show the Opposite Change

Some older books recognise Sphenodon guntheri, often called Günther’s tuatara, as a second species.

Later research supported treating tuatara as one species. New Zealand’s Department of Conservation explains that the two-species treatment was discontinued in 2009.

In one case, a previously broad species was divided. In the other, previously separated animals were brought together.

Neither direction is automatically right. What matters is how well the classification fits the evidence.

Being the Only Species and Being Threatened Are Different Questions

If the sole living species in a family becomes extinct, that family loses all its living representatives.

However, the classification alone does not tell us how likely that loss is. Extinction risk depends on population trends, distribution, habitat and the pressures affecting the species.

Reading the Conservation Categories

The IUCN Red List assesses extinction risk. The categories used below are Least Concern (LC), Vulnerable (VU), Endangered (EN) and Critically Endangered (CR). Vulnerable, Endangered and Critically Endangered are collectively described as threatened categories.

The following table presents the global assessments cited for this article. The years identify those assessments; the table should not be read as saying that every species was reassessed in 2026.

Species	Global IUCN category cited	Assessment year
Leatherback turtle	Vulnerable (VU)	2013
Pig-nosed turtle	Endangered (EN)	2017
Central American river turtle	Critically Endangered (CR)	2006
Chinese crocodile lizard	Endangered (EN)	2014
Earless monitor lizard	Endangered (EN)	2019
Florida worm lizard	Least Concern (LC)	2007
Red pipe snake	Least Concern (LC)	2013
Mexican burrowing python	Least Concern (LC)	2012
Madagascar blind snake	Critically Endangered (CR)	2011
Tuatara	Least Concern (LC)	2019

Least Concern does not mean that an animal faces no problems anywhere. Likewise, sharing a threatened category does not mean that two species need the same conservation measures.

Different Lives, Different Threats

For the Central American river turtle, capture for food is a major concern. Removing large breeding adults also removes animals that could produce future generations. Its Critically Endangered assessment reflects severe pressures on the species.

For the Chinese crocodile lizard, protecting wooded streams and reducing capture for the pet trade address important threats.

For tuatara, introduced mammals are a central concern. Rats eat eggs and young and can affect the small animals available as food. Keeping introduced mammals away from island refuges is therefore an important part of conservation.

Leatherbacks face hazards including accidental capture in fishing gear, loss of nesting habitat and marine debris. Their journeys across national boundaries also make international cooperation important.

“One living species in a family” is a common feature. It is not a common conservation plan.

Global and Regional Assessments Can Differ

A widespread species may face very different conditions in different parts of its range.

The leatherback illustrates this clearly. In the 2013 IUCN assessments, it was classified as Vulnerable globally, while the East Pacific subpopulation was Critically Endangered. A subpopulation is a geographically or otherwise distinct part of the species’ overall population.

These assessments answer questions at different scales. Neither cancels out the other.

When reading a conservation category, check three things:

• Which species or population was assessed?
• What geographical area does the assessment cover?
• When was the assessment made?

Together, those details make a short label much more informative.

Extinction Risk and Trade Rules Have Different Jobs

Conservation systems also serve different purposes.

System	Main purpose
IUCN Red List	Assesses extinction risk
National and regional red lists	Assess status within a defined country or region
CITES	Regulates international trade in listed wild animals and plants

Being threatened on the IUCN Red List is not the same as being regulated under CITES.

For example, a species’ IUCN category describes its assessed extinction risk, while its CITES listing concerns international trade. Knowing which system a label belongs to helps us understand what it is—and is not—telling us. NOAA’s leatherback account presents legal listings separately from the species’ biology and threats.

One Shared Feature, Ten Different Lives

A leatherback’s ridged shell, a worm lizard’s shovel-like head and a tuatara’s rows of teeth all invite a closer look.

These ten reptiles share an unusual classification pattern. Their bodies reveal very different ways to live.

Their stories also show how we come to know them. A stomach preserved in a specimen can reveal a meal. A CT scan can uncover bones beneath scales. A precise locality can connect an old museum specimen with a living population.

Classification brings evidence together to describe differences and relationships. As that evidence grows, species may be separated or brought together.

The next time you encounter an unfamiliar reptile in a photograph, a field guide or a museum display, choose one detail and follow the question it raises.

Why that shape? How does it help the animal live? What evidence allows us to tell?

Books from ECO LIFE PLANET

The Forest Museum Kindle series explores classification and natural history in greater depth.

The following books are in Japanese. The English titles below are descriptive translations.

• An Introduction to Taxonomy: The Basics of the Science of Organising the World, Level 1
  View on Amazon Japan
• A Spring Nature Observation Handbook: Fieldwork for Children and Adults
  View on Amazon Japan
• One Family, One Genus, One Species: The Narrowest Branches of the Tree of Life — Taxonomy Edition
  View on Amazon Japan

These links are Amazon affiliate links.

References

• The Reptile Database — Species database
• NOAA Fisheries — Leatherback Turtle
• Naturalis — Turtles of the World: Carettochelys insculpta
• IUCN/SSC Tortoise and Freshwater Turtle Specialist Group — Dermatemys mawii, 058 (2012)
• Bishop et al. — Diet of Dermatemys mawii, an Aquatic Turtle That Relies Heavily on Terrestrial Vegetation (2022)
• ZSL EDGE of Existence — Chinese Crocodile Lizard
• DigiMorph, University of Texas at Austin — Lanthanotus borneensis (2001)
• Journal of Herpetology — Evidence of Population Genetic Structure within the Florida Worm Lizard (2005)
• Maschio et al. — Food habits of Anilius scytale in the Brazilian Amazonia (2010)
• Reptiles of Ecuador — Pipe Snake: Anilius scytale (2024)
• Wegener et al. — Morphological variation and taxonomic reassessment of the endemic Malagasy blind snake family Xenotyphlopidae (2013)
• New Zealand Department of Conservation — Tuatara
• Te Ara — Teeth: Tuatara (2009)
• Liang et al. — Taxonomic revision of the critically endangered big-headed turtles, with description of a new species (2025)
• IUCN SSC Marine Turtle Specialist Group — New Leatherback Red List Assessments Published (2013)