This is a ranking of all countries of the world with at least one recorded species of Opiliones. Numbers are taken from my forthcoming Catalog of Opiliones of the World, which is an ongoing project, so they are subject to change with more exhaustive parsing (especially for Europe, with many small countries for which small faunistic papers abound, making it very difficult to keep up). Fossils are not included. Subspecies are counted as species. Thanks to Solanlly Carrero, Emanuel Delfosse, Carlos Prieto, Gabriel de los Santos and Anna Šestáková for input.

Names of the countries used here are only for reference and I do not support any claims as to sovereignty and other political issues. No opinion about boundaries of litigious areas is intended and no political slogans are present here, rather the traditional view of the literature is in general followed. The name “Macedonia” is used here for the former Yugoslav Republic of Macedonia, just because 20th century taxonomic literature used this name for a region of Yugoslavia. I do not endorse any side of the endless Graeco-Macedonian dispute over the name. Only for the sake of historical-biogeographic-bibliographic continuity, in this work:

1. Abkhazia and South Ossetia are included in Georgia;
2. Chechnya is included in Russia;
3. Crimea is included in Ukraine;
4. Donetsk People's Republic is included in Ukraine;
5. French Guiana is treated as an independent country;
6. Kawthoolei is included in Burma;
7. Kosovo is included in Serbia;
8. Luhansk People's Republic is included in Ukraine;
9. Nagorno-Karabakh is included in Azerbaijan;
10. Palestine is included in Israel;
11. Southern Cameroons (Ambazonia) is included in Cameroon;
12. The areas of Iraq, Lebanon, Syria controlled by the Islamic State of Iraq and the Levant (ISIL) are not recognized here as ISIL, but as part of these countries;
13. Tibet is included in China (People's Republic of China);
14. Taiwan (Republic of China) is NOT included in China (People's Republic of China);
15. Transnistria is included in Moldova;
16. Turkish Republic of Northern Cyprus  is included in Cyprus;
17. Wa State is included in Burma.

There are currently 23 countries in the world that have 100 or more valid species of Opiliones. Brazil is by far the most diverse of them, with more than 1000 species, which is a combination of natural diversity (comparing, the whole Europe has only 350 species) and concentration of studies. Venezuela surprisingly stands as the runner up, because of the immense descriptive effort by González-Sponga, while neighbor countries such as Colombia occupy much humbler places due to undersampling. African countries are poorly represented, being perhaps the greatest global undersampling. Some very large countries such as Russia (74 species) do not come even close to the top 20; on the other hand, a small country such as Japan has more than 100 species due to the effort of local researchers (mainly Suzuki and Tsurusaki). Local opilionologists (other examples: Lawrence in S.A. and Forster in NZ) therefore play an important role in the diversity assessment of a country.

The expressive percentage of endemic species reflects the poor dispersal abilities of harvestmen, especially in continents oriented in the North-South axis. In Eurasia, which is oriented in the sense West-East, which brings more uniform climate, the percentage of endemic species drops drastically. As examples, the most diverse countries of Asia and America all have more than 80% of their species endemic. Even of the more than a thousand Brazilian species, 95% are endemic. In Europe, most countries have less than 10% of endemics, many of them have zero endemics. Not by coincidence, the European countries with more endemics are those oriented North-South such as Italy and Portugal (almost 40% each). In large, isolated islands/archipelagos, such as Madagascar and New Zealand, the percentage of endemics is 100%.

Estimative of percentage of described species in South America. Based on decades of sampling in South America, always discovering new species, and on the number of undescribed species in collections, one may safely estimate that in the Atlantic forest only 75-85% of the species has been formally described. In the semi-arid diagonal, the diversity is naturally lower, but we may estimate similar numbers. For the Andean and Amazonian areas, the degree of knowledge is less, we may have around 50% or less of the species described. For undersampled areas such as Bolivia, probably less than 30% of the diversity is described. The revisionary papers constantly propose synonymies which almost cancel out the number of new species described.

Gagrella

 238

Psathyropus

 42

Cynorta

 154

Metabiantes

 41

Leiobunum

 132

Sabacon

 40

Prionostemma

 119

Ischyropsalis

 39

Paecilaema

 93

Opilio

 39

Geaya

 84

Eusarcus

 36

Nemastoma

 84

Discocyrtus

 76

Phareicranaus

 35

Zaleptus

 72

Dentobunus

 34

Gagrellula

 67

Eucynorta

 34

Nuncia

 61

Avima

 33

Gnomulus

 54

Rhampsinitus

 47

Erginulus

 32

Nelima

 45

Tithaeus

 32

Zalmoxis

 45

Cynortula

 31