A Strange 99-Million-Year-Old Arachnid Trapped in Amber: Could It Be a New Species?
By Keith Sturgeon
Guest Contributor | Amber Bugs
An Ancient Arachnid With Strange Hooks Raises New Questions
Every so often, a fossil comes along that challenges our expectations. Something so unusual that even deciding what kind of creature we are looking at becomes an adventure. Enter this arachnid with backward-facing hooks in it's pedipalps (arms).
This remarkable arachnid, preserved in approximately 99-million-year-old Burmese amber from Myanmar, may be one of those discoveries. In this blog we will investigate the inclusion, including contacting an exciting expert in fossil spiders, Jörg Wunderlich, a german spider fossil specialist.
At AmberBugs, one of our greatest pleasures is encountering fossil organisms that refuse to fit neatly into our expectations.
This specimen is an extraordinary example.Which species is it? And what are these hooks used for? Could we be looking at something entirely unknown to science?
At first glance, it looks like a spider. But the closer we examine it, the stranger it becomes.
It has some highly unusual body parts: Very large chelicerae (mouthparts), long-reaching pedipalps (hands), and unusual backward-facing hooks (unknown use) on those pedipalps. Not to mention it's extraordinarily long legs.
There are species with similar features in the fossil record: Assassin spiders, tailless whip scorpions, and armored huntsmans being the most similar in body shape.
Or something new?
Let's take a closer look at this arachnid in amber
Its remarkable chelicerae (mouthparts) are unusually large, with clearly preserved teeth and fine sensory hairs. Their prominent size and curved shape suggest they may have been specialized for grasping and holding prey in place.
Especially intriguing are the elongated pedipalps, which bear unusual backward-facing hooks. It almost looks as though this arachnid has two large hooks extending from its arms. What purpose could these mysterious structures have served?
These unusual features raised questions about the specimen's identity. To investigate, we compared its anatomy with several groups of living and extinct arachnids.
Now, let's see what species this arachnid might be!
The Tailless Whip Scorpion Connection
Perhaps the most visually striking comparison is with the amblypygids, commonly called tailless whip scorpions. These extraordinary arachnids possess extremely long legs and powerful, specialized pedipalps used to capture and restrain prey.
Tailless Whip Scorpion Amber Inclusion Resembling Tailless whip scorpion
In living amblypygids, the first pair of legs is modified into exceptionally long sensory appendages, while the pedipalps are equipped with formidable spines.
Our specimen’s elongated appendages and unusual hooks immediately bring these creatures to mind.
Could the structures we are interpreting as hooked pedipalps represent a related form of prey-capturing apparatus?
Possibly, but there are substantial anatomical questions.
Amblypygids possess a distinctive flattened body, raptorial pedipalps, and specialized sensory legs. Their chelicerae also differ considerably from the elongated structures associated with assassin spiders.
At this stage of the investigation, we could not demonstrate the complete combination of features necessary to confidently place this fossil among the amblypygids.
Nevertheless, the resemblance was intriguing enough to warrant serious consideration.
The Assassin Spider Connection
Assassin spiders, members of the family Archaeidae, are among the most extraordinary predatory spiders ever to evolve. Our amber specimen immediately invites comparison.
Assassin Spider Amber Inclusion Resembling Assassin Spider
Their most recognizable feature is their unusual feeding apparatus. Many possess elongated chelicerae and a highly modified head region, allowing them to seize prey while keeping it at a distance from their bodies.
Assasin Spider Amber Inclusion Resembling Assassin Spider
Assassin spider (Archaeidae) | Photograph by Hannah Wood, Smithsonian National Museum of Natural History. Original source.
The long, forward-projecting chelicerae on our specimen are perhaps the most compelling similarity. Their apparent proportions and positioning suggest a specialized method of capturing or manipulating prey.
The specimen’s long, slender legs also contribute to its assassin-spider-like appearance.
However, there are problems with this identification.
Typical assassin spiders possess a distinctive elevated cephalic region, often described as a neck, along with characteristic cheliceral arrangements. These features have not yet been conclusively demonstrated in our specimen.
Even more intriguing are the long pedipalps bearing what appear to be backward-facing, possibly articulated hooks. These are not features we would ordinarily expect on a typical assassin spider.
So while the chelicerae suggest Archaeidae, other structures seem to point elsewhere.
The Armored Huntsman Connection
Another fascinating possibility is an affinity with the extinct armored huntsman spiders, members of the extinct family Lagonomegopidae.
These remarkable Cretaceous spiders are particularly well represented in Burmese amber. They were part of an ancient spider lineage that disappeared long before the modern world.
Armored huntsman spiders are known for their unusual body proportions, often robust legs, and distinctive arrangements of eyes and body structures.
Our specimen’s exceptionally long legs and apparently enlarged posterior walking legs raise interesting questions about its locomotion and hunting behavior.
Could these proportions indicate an animal adapted for rapidly navigating the branches, bark, and vegetation of a Cretaceous forest?
There are similarities worth investigating, but important differences remain.
The unusually elongated chelicerae, and especially the hooked pedipalps, are not an obvious match for the familiar lagonomegopid body plan.
A definitive comparison will require a careful examination of the eyes, carapace, leg articulations, and other diagnostic structures.
A new species of arachnid found in amber?
Perhaps none of these comparisons provide an identification. Perhaps it belongs to a psecies which has never been identified?
It is possible that we are looking at an unusual extinct lineage, perhaps even a form not previously described.
The Hooks: Perhaps the Most Fascinating Feature of All
Of all the unusual structures visible in this fossil, the backward-facing hooks on the pedipalps may ultimately prove the most revealing.
They appear to be positioned in a way that could allow them to engage, grasp, or restrain another structure.
Their precise articulation and function were initially uncertain, but one particularly interesting possibility deserved attention.
Could these hooks indicate that our specimen was a male?
In certain living arachnids, males possess specialized appendages used during courtship and mating. In some groups, these structures allow the male to physically grasp, hold, or control the female’s chelicerae during mating.
The hooks in our fossil suggest a potentially similar function.
The male and female position their chelicerae together, sometimes locking them during copulation.
If these structures were used to engage a female’s chelicerae, they may represent a form of sexually specialized anatomy rather than an adaptation for capturing prey.
This would make our specimen especially interesting, because we might be looking at not merely an unusual predator, but also evidence of reproductive behavior preserved in anatomy nearly 100 million years old.
Their apparent orientation, placement, and possible mobility make a reproductive function a compelling possibility.
If that interpretation proves correct, the fossil may very well represent a male with highly specialized mating structures.
The Mystery Deepens: A 99-Million-Year-Old Spider May Have a Name
Following our initial examination, I contacted arachnid specialist and author Jörg Wunderlich, whose extensive work on fossil spiders includes the description of Loxoderces, a genus placed in the family Burmosolidae, in 2017.
The correspondence has helped bring the specimen’s unusual reproductive anatomy into sharper focus.
The structures that initially appeared to be backward-facing claws are associated with the male reproductive apparatus. Of particular interest is the embolus, a specialized component of the male spider’s pedipalp involved in transferring sperm during mating.
This is an important distinction. What initially appeared to be a predatory adaptation may also represent reproductive specialization.
These structures may have served a mechanical purpose: grasping or stabilizing the female’s chelicerae, or fangs, during sperm transfer.
The apparent shape and orientation of these structures make this an intriguing possibility. It could suggest a specialized mating behavior in a spider that lived nearly 100 million years ago.
A Remarkable Resemblance to Spiniarchaea aberrans
During further consideration of the specimen, my attention turned toward another unusual fossil spider described by Dr. Wunderlich: Spiniarchaea aberrans.
Spiniarchaea aberrans Spiniarchaea aberrans
Spiniarchaea aberrans – Fossil spider preserved in Cretaceous Burmese amber. Images from Wunderlich and Müller (2021), Beiträge zur Araneologie, Volume 14.
Amber inclusion resembling Spiniarchaea aberrans Amber inclusion resembling Spiniarchaea aberrans
Our specimen bears a striking affinity to this remarkable arachnid.
The combination of its unusual anterior anatomy, elongated appendages, and specialized male palpal structures makes this comparison particularly intriguing.
Could our specimen belong to this lineage, or perhaps represent a closely related but previously unknown species?
At that stage, the question remained unanswered.
I contacted Dr. Wunderlich again to request his opinion on this possible new direction in our investigation.
The Expert Has Spoken: Loxoderces
After further correspondence with Dr. Wunderlich, we have received an expert opinion on the identity of our remarkable fossil.
This is apparently an exceptional example of what most certainly is from the genus Loxoderces.
No indication of a species was provided, leaving the possibility that it may be undescribed.
After considering assassin spiders, armored huntsman spiders, amblypygids, and the intriguing resemblance to Spiniarchaea aberrans, our specimen now appears to have found its place within the genus Loxoderces.
Comparison of Loxoderces and our specimen
Below are photos of Jörg Wunderlich's Loxoderces specimen, placed alongside our specimen.
Loxoderces Amber specimen resembling loxoderces
Loxoderces Amber specimen resembling loxoderces
The question of its species, however, remains open.
As for the name, I have a suggestion: Hook Spider.
Why This Specimen Matters
What makes this fossil especially fascinating is not simply its unusual appearance, but the possibility that it preserves evidence of reproductive specialization in an extinct Cretaceous spider. In other words, spider sexual organs.
The fossil record often provides extraordinary detail about the external anatomy of ancient organisms. It is much less common for that anatomy to offer meaningful clues about their reproductive behavior.
Here, the unusual male palpal structures may provide just such an opportunity.
And if it represents an undescribed species, it may add another remarkable chapter to our understanding of spider evolution during the Cretaceous.
It raises questions about predation, locomotion, reproductive specialization, and the diversity of arachnids living in the forests of Cretaceous Myanmar.
What began as a mystery involving several very different arachnid groups has now led us to Loxoderces, an extinct genus described by Dr. Wunderlich.
For now, the identification has become considerably clearer, although the possibility of a previously undescribed species remains an exciting question for further investigation.
And that is precisely what makes this specimen so incredibly interesting.
Are you a fossil lover? Do you have anything to add to this specimen's identification? Email us and comment below.
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Possible Loxoderces arachnid in amber
References and Image Credits:
Wunderlich, J. (2017). New and rare fossil spiders (Araneae) in Mid Cretaceous Amber from Myanmar (Burma), including the description of new extinct families of the suborders Mesothelae and Opisthothelae, as well as notes on the taxonomy, the evolution and the biogeography of the Mesothelae. Beiträge zur Araneologie, 10, 72–279, 333–354.
Smithsonian National Museum of Natural History. (n.d.). Spiders as predators. Smithsonian Institution. Photograph by Hannah Wood. https://naturalhistory.si.edu/education/teaching-resources/life-science/spiders-predators
Penney, D. (2006). The oldest lagonomegopid spider, a new species in Lower Cretaceous amber from Álava, Spain. Geologica Acta, 4(3), 377–382. https://doi.org/10.1344/105.000000351
WanderingMogwai. (2015). Filmy dome spiders (Neriene radiata) mating [Photograph]. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Filmy_dome_spiders_(Neriene_radiata)_mating.jpg. Licensed under CC BY-SA 4.0. https://creativecommons.org/licenses/by-sa/4.0/?utm_source=chatgpt.com
Asian Society of Arachnology. (2022, December 29). Embolus. Arachnological Glossary. https://www.asianarachnology.com/glossary/embolus/
Wunderlich, J., & Müller, P. (2021). Descriptions of new fossil spiders (Arachnida: Araneae) in Late (Mid) Cretaceous Burmese amber with focus on the superfamilies Palpimanoidea and Deinopoidea and members of the RTA-clade, as well as remarks on palaeobehaviour, palaeofauna, taxonomy and phylogenetics. Beiträge zur Araneologie, 14, 25–262. https://www.joergwunderlich.de/Downloads/Beitr._Araneol._Band_14_%282021%29.pdf
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