Chamaeleo intermedius

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Chamaeleo intermedius
Temporal range: Miocene 14  Ma
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Chamaeleo intermedius.jpg
Reconstruction of Chamaeleo intermedius
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Iguania
Family: Chamaeleonidae
Genus: Chamaeleo
Species:
†C. intermedius
Binomial name
†Chamaeleo intermedius
Hillenius, 1978

Chamaeleo intermedius is an extinct species of chameleon from the Miocene of Kenya. It was given its name based on the fact that it shares traits with both species of the genus Chamaeleo and those of Trioceros , which at the time were placed in the same genus. This belief that it was an intermediate form was however rejected by later research.

Contents

History and naming

Type specimen of ''Chamaeleo intermedius'', bottom row shows the dorsal knobs in different perspectives Chamaeleon intermedius.png
Type specimen of ''Chamaeleo intermedius'', bottom row shows the dorsal knobs in different perspectives

The holotype of Chamaeleo intermedius, specimen KNM-FT 3833, was discovered at a paleontological site near Fort Ternan in Kenya. It consists of a well preserved calcite cast [1] [2] that preserves the entire head and parts of the upper body, cut off by an almost straight line ranging from the throat to approximately the halfway point of the back. The fossil material was recognized as a chameleon and subsequently described by Hillenius in 1978, after having been given the material by Richard Erskine Frere Leakey. [3]

The species name "intermedius" was chosen due to the belief that Chamaeleo intermedius may represent a missing link between the group around the common chameleon and those around the side-striped chameleon, the later of which are now regarded as forming the distinct genus Trioceros . [3] In a later publication it is argued that this name would be quite ironic, as the species was found to fit more comfortably into just one of the two groups. [4]

Description

Chamaeleo intermedius was a relatively small chameleon based on the fossil material, which is only 4.3 cm (1.7 in) long from the head to the middle of the torso. However it clearly exhibits traits typically associated with the genus Chamaeleo including the higher than broad body, well developed keel along the back, large eyes, helmet-like casque, well defined parietal crest and the presence of a swollen throat pouch likely containing the characteristic projectile tongue these reptiles are known for. Only a small section of an arm is preserved, which matches the narrow nature of chameleon limbs. Parts of the upper lip were curled up during preservation, revealing two different tooth morphologies. Teeth towards the front show three cusps while other teeth are composed of a single cone surrounded by a cup. The type description notes that Chamaeleo intermedius preserves no traits unique to this species, but is instead defined based on the combination of features. [3]

The casque or helmet of Chamaeleo intermedius is formed by a well developed and elevated parietal crest and what was originally described as temporal crests on either side of the skull. However a later publication by Klaver argued that these temporal crests may in fact have been misidentified lateral crests based on their resemblance to the same structure in the Namaqua chameleon. [4] The canthi rostralis between the eyes and snout is also well developed. The casque ascends relatively gradually before descending abruptly towards the neck. Both the forked parietal and temporal crests are lined by conic tubercles, which are also present around the eyesockets. The back of this species is lined by a double row of scales, however around the neck some larger scales form structures similar to the dorsal ridge seen in the Namaqua chameleon or the Mount Lefo chameleon. The later was especially highlighted as its dorsal ridge was also composed of two scale rows. Similar but smaller structures are also found further back on the body. Besides this scale structures and the double row along the back, the scales of this species are generally homogenous and of similar size and shape across the body. Chamaeleo intermedius preserves no crest along its throat, no lateral crests or occipital lobes attached to the casque and no other ornaments such as brow or nose horns. [3]

In regards to the homogenous scales, dorsal knobs, lack of a throat crest and elevated parietal crest it resembles the modern Namaqua chameleon from southern Africa. The two differ however as the modern species has irregular dorsal scales, an unforked parietal crest and a head and body that are both notably broadened. The dorsal knobs of Chamaeleon intermedius also bear resemblance to those found in some Mount Lefo chameleons. The list of differences between the two is however greater, as the Mount Lefo chameleon has varying scale size across the body, a throat crest, both temporal and lateral crests and a flat casque. The overall crest anatomy of the fossil species is generally similar to the side-striped chameleon and species related to it such as the Jackson's chameleon, Werner's chameleon, Ngosi Volcano chameleon as well as the tiger chameleon. Here too several differences were however noted, including the heterogenous scales of the body, presence of a gullar crest and form of the dorsal crest. [3]

Classification

When described, Chamaeleo intermedius was firmly placed in the extant genus Chamaeleo . Specific attention is drawn to its anatomy displaying a mix of features between two groups within the genus, those surrounding the common chameleon and Namaqua chameleon and those surrounding the side-striped chameleon. However, in recent years the later group has been deemed distinct enough to warrant its own independent genus, now named Trioceros . [5] This may be resolved by observations made by Klaver. Klaver argues that the temporal crest of Chamaeleo intermedius may in fact be homologous to the lateral crest of the Namaqua chameleon and furthermore goes on to say that forked parietals are also known in species of the Chamaeleo group and not exclusive to what is now Trioceros. Subsequently, the argument is made that Chamaeleo intermedius, in spite of its name, fits neatly into the genus Chamaeleo and may in fact not be the transitional form it was initially thought to be. [4]

Related Research Articles

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<i>Bradypodion</i> Genus of lizards

Bradypodion is a genus of chameleons in the family Chamaeleonidae, collectively called South African dwarf chameleons. All species are found in South Africa and most are endemic to this country, but a few can also be found in Eswatini, Lesotho, southernmost Namibia and possibly southernmost Mozambique. They are quite small chameleons where the different species often can be difficult to separate by appearance, although exact location and the intense breeding colours of males are useful for their identification. They are arboreal, but some species are mostly found low in the vegetation.

<i>Chamaeleo</i> Genus of lizards

Chamaeleo is a genus of chameleons in the family Chamaeleonidae. Most species of the genus Chamaeleo are found in sub-Saharan Africa, but a few species are also present in northern Africa, southern Europe, and southern Asia east to India and Sri Lanka.

<span class="mw-page-title-main">Jackson's chameleon</span> Species of lizard

Jackson's chameleon, also known as Jackson's horned chameleon, three-horned chameleon or Kikuyu three-horned chameleon, is a species of chameleon native to East Africa, and introduced to Hawaii, Florida, and California.

<span class="mw-page-title-main">Namaqua chameleon</span> Species of lizard

The Namaqua chameleon is a ground-living lizard found in the western desert regions of Namibia, South Africa and southern Angola.

<span class="mw-page-title-main">Indian chameleon</span> Species of lizard

The Indian chameleon is a species of chameleon found in Sri Lanka, India, Pakistan and select other parts of South Asia. Like other chameleons, this species moves slowly with a bobbing or swaying movement and are usually arboreal. They have an extremely long and sticky tongue, which they use to catch insects from several feet away. Also like other chameleons, C. zeylanicus has bifurcated feet with a tongs-like shape, a prehensile tail, independent eye movement, and the ability to rapidly change skin colouring and patterns. Despite common misconceptions, they do not change their visual appearance based on their surroundings or background, or even for camouflage, and may not even be able to perceive colour differences; rather, it is primarily for communication with others of their species, including to signify the receptiveness of a female or submissiveness in general disputes. Additionally, colouring can change for controlling body temperature, changing to darker colours to absorb heat, or lighter to cool themselves.

<i>Kinyongia</i> Genus of lizards

Kinyongia is a genus of chameleons found in montane and sub-montane areas in Kenya, Tanzania, Uganda, Rwanda, Burundi, and far eastern DR Congo. They are restricted to forests, woodlands and other wooded habitats, and many species have very small geographic ranges. In most species, at least the males have horns or knobs on their noses. As typical of most chameleons, Kinyongia are oviparous.

<i>Trioceros</i> Genus of lizards

Trioceros is a genus of lizards in the family Chamaeleonidae, the chameleons, native to lowlands and highlands in the African mainland, ranging from Ethiopia south to Mozambique and west as far as Ghana. Trioceros was considered a subgenus of the genus Chamaeleo until 2009, when it was elevated to full genus level.

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<i>Trioceros hoehnelii</i> Species of lizard

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<span class="mw-page-title-main">Owen's chameleon</span> Species of lizard

Owen's chameleon, also commonly known as Owen's three-horned chameleon, is a species of lizard in the family Chamaeleonidae. The species is native to forests in central Africa. Named after British naval officer and explorer William Fitzwilliam Owen, it was first described in 1831 by the naturalist John Edward Gray, and is the type species of the genus Trioceros.

<span class="mw-page-title-main">Four-horned chameleon</span> Species of lizard

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Trioceros schubotzi, the Mt. Kenya side-striped chameleon or Mt Kenya dwarf chameleon is a species of chameleon that was found on Mt. Kenya and originally regarded as a lectotype designation. Many finding on this species were conducted by Germans, so many of the manuscripts written about them are very old and not much has been researched on this particular species. The locality of this species can be confirmed to Mt. Kenya.

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<i>Trioceros ellioti</i> Species of lizard

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<i>Trioceros wolfgangboehmei</i> Species of lizard

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References

  1. ↑ Rieppel, O.; Walker, A.; Odhiambo, I. (1992). "A Preliminary Report on a Fossil Chamaeleonine (Reptilia: Chamaeleoninae) Skull from the Miocene of Kenya". Journal of Herpetology. 26 (1): 77. doi:10.2307/1565027. JSTOR   1565027.
  2. ↑ Čerňanský, A.; Herrel, A.; Kibii, J.M.; Anderson, C.V.; Boistel, R.; Lehmann, T. (2020). "The only complete articulated early Miocene chameleon skull (Rusinga Island, Kenya) suggests an African origin for Madagascar's endemic chameleons". Scientific Reports . 10 (1): Article number 109. Bibcode:2020NatSR..10..109C. doi:10.1038/s41598-019-57014-5. PMC   6954250 . PMID   31924840.
  3. 1 2 3 4 5 Hillenius, D. (1978). "Notes on Chameleons IV. A New Chameleon, from the Miocene of Fort Ternan, Kenya (Chamaeleonidae, Reptilia)". Beaufortia. 28 (343): 9–15.
  4. 1 2 3 Klaver, C. J. J. (1981). "Lung-morphology in the Chamaeleonidae (Sauria) and its bearing upon phytogeny, systematics and zoogeography". Journal of Zoological Systematics and Evolutionary Research. 19 (1): 36–58. doi: 10.1111/j.1439-0469.1981.tb00231.x .
  5. ↑ Tilbury, C.R.; Tolley, K.A. (2009). "A re-appraisal of the systematics of the African genus Chamaeleo (Reptilia: Chamaeleonidae)". Zootaxa. 2079 (57–68): 57–68. doi:10.11646/zootaxa.2079.1.2.
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