Armadillidium, Brandt, 1831

Cifuentes, Julio, Robla, Jairo & Garcia, Lluc, 2024, Description of Armadillidium boalense sp. nov. from northern Spain, with remarks and a key of the genus in the Iberian Peninsula and the Balearic Islands (Isopoda: Oniscidea: Armadillidiidae), Zootaxa 5497 (1), pp. 83-99 : 96-97

Key to the Iberian-Balearic species of the genus Armadillidium

Identification key of the Armadillidium species recorded in the Iberian Peninsula and the Balearic Islands. Mainly based on Schmölzer (1954; 1965); Vandel (1960; 1962); Cruz (1990; 1993); Cruz & Dalens (1990); Garcia (2003; 2020); Garcia & Cabanillas (2021); Cifuentes & Escarabajal (2022a, 2022b) and the present study. A. scabrum Dollfus, 1892 , (only known from Seville) is excluded due to insufficient information in its original description ( Dollfus, 1892). The distribution is indicated only for the endemic species.

1. Head of duplocarinate type, with scutellar and post-scutellar ridges.............................................. 2.

- Head of ‘ Armadillidium -type’ without scutellar ridge (linea frontalis)........................................... 13.

2. Conglobation ability of eusphaeric type (living animals can roll into a perfect ball). Integument smooth or weakly granulated................................................................................................... 3.

- Conglobation ability of pseudo/mesosphaeric type (living animals can roll into an ovoid or imperfect ball, respectively). Integument smooth, granulated or with spiniform tubercles.................................................... 6.

3. Telson triangular. Living animals with a vivid coloration, usually with yellowish muscle spots on a dark background. Integument smooth or slightly granulated............................................................................ 4.

- Telson trapezoidal. Very little or no pigmented body. Integument smooth, covered with bristle-like scale-setae. Male pereopod 7 with ventrally concave ischium and a protruded distal knob on the basis. Strictly littoral species... A. album Dollfus, 1887 .

4. Male pleopod 1 endopod with distal third bent 90º outward. Exopod with notched tracheal field..... A. pictum Brandt, 1833 .

- Male pleopod 1 endopod long and straight, only slightly bent apically............................................ 5.

5. Male pleopod 1 exopod without posterior lobe, twice as wide as long and with notched tracheal field. Galicia and Cantabric region ...................................................................... A. galiciense Schmölzer, 1955 .

- Male pleopod 1 exopod with triangular posterior lobe, almost as long as wide, and with notched tracheal field. Asturias ......................................................................................... A. boalense sp. nov.

6. Integument smooth.................................................................................... 7.

- Integument with large or spiniform tubercles................................................................ 9.

7. Telson trapezoidal, with a wide posterior margin and straight lateral edges. Menorca (Balearic Islands).................................................................................................. A. strinatii Vandel, 1961 .

- Telson triangular...................................................................................... 8.

8. Lateral edge of first the pereon-tergite, angulate. Male pereopod 7 without distinct sexual modification.Mallorca and surrounding islets (Balearic Islands)................................................................ A. cruzi Garcia, 2003 .

- Lateral edge of the first pereon-tergite regularly curved. Male pereopods 6-7 with a marked distal knob on ischium; male pereopod 7 with ventrally concave ischium. Levantine Iberian region......................... A. espanyoli Cruz, 1992 .

9. Telson trapezoidal.................................................................................... 10.

- Telson triangular..................................................................................... 12.

10. Telson with narrow posterior edge, rounded posterior angles and concave lateral edges; back covered with large conical tubercles; scale-setae with forked setae. Male pleopod 1 exopodite with short posterior lobe and notched tracheal field. Endemic from Murcia region ............................................... A. ibericum Cifuentes & Escarabajal Bernabé, 2022 .

- Telson with broad posterior edge, obtuse posterior angles and straight lateral edges; scale-setae tricorn-type, without forked setae.............................................................................................. 11.

11. Cephalon with angled postscutellar ridge. Pleonites with a transverse row of strong granulations. Male pleopod 1 exopodite twice as wide as long, with barely prominent posterior lobe. Menorca (Balearic Islands)..... A. serrai Cruz & Dalens, 1990 .

- Cephalon with regularly arched post-scutellar ridge. Pleonites without apparent granulations. Exopodite of the male pleopod 1 with distinct posterior lobe. Pre-Pyrenean Iberian region................................... A. nahumi Garcia, 2020 .

12. Cephalon with strongly angulate post-scutellar ridge; scutellar ridge, complete. Back covered with hypertrophic spiniform tubercles. Telson broad and short, with broadly rounded apex. Mallorca (Balearic Islands).......... A. pretusi Cruz, 1992 .

- Cephalon with regularly arched post-scutellar ridge; scutellar ridge incomplete. Body covered with spiny tubercles. Telson narrow, with straight lateral sides................................................ A. serratum Budde-Lund, 1885 .

13. Telson trapezoidal.................................................................................... 14.

- Telson triangular..................................................................................... 15.

14. Conglobation ability of mesosphaeric type. Male pleopod 1 exopod with sinuous inner margin; endopod straight. Male pereopod 7 with a rounded distal bulge on ischium.............................................. A. sordidum Dollfus, 1887 .

- Conglobation ability of eusphaeric type. Male pleopod 1 exopod with convex inner margin; endopod distally curved. Male pereopod 7 without distal bulge on ischium........................................... A. vulgare ( Latreille, 1804) .

15. Conglobation ability of mesosphaeric type. Back granulated. The posterior edge of the first pereon-tergite forms angles at the limit with the epimera............................................................ A. granulatum Brand, 1833.

- Back smooth or with very weak granulations.............................................................. 16.

16. Conglobation ability of pseudosphaeric type. Frontal shield almost twice as long as wide, very prominent above the vertex. The posterior margin of the first pereon-tergite forms angles at the limit with the epimera........ A. nasatum Budde-Lund, 1885 .

- Conglobation ability of mesosphaeric type. Frontal shield slightly prominent and directed backwards above the vertex. Posterior margin of first pereon-tergite regularly sinuous............................................................. 17.

17. Male pleopod 1 exopod with very short posterior lobe................................ A. assimile Budde-Lund, 1885 .

- Male pleopod 1 exopod with well-developed posterior lobe.............................. A. arcangelii Strouhal, 1929 .

* Note that Armadillidium mateui Vandel is not currently included in the genus Armadillidium . This species has been transferred to Alloschizidium Verhoeff (see Cifuentes 2022). Thus, it was not included in the identification key.